Ofcom said it is investigating an unspecified complaint against the reality TV show.
The reality series, in which single people are matched and married to complete strangers, was investigated by the BBC's Panorama earlier this year.
Its report, broadcast in May, included allegations by two women that they had been raped during production of the show. Another woman alleged a non-consensual sexual act.
All three said the Channel 4 show, made by production company CPL, did not do enough to protect them.
The three men have denied the allegations.
On Monday, an Ofcom spokesperson said it is "investigating a fairness and privacy complaint about Married At First Sight UK".
It is understood the complaint has come from a person or organisation that took part in the show.
Ofcom has also looked into a complaint of unjust or unfair treatment on MAFS, the Press Association understands.
A male MAFS UK cast member was arrested in June on suspicion of rape and bailed, the Metropolitan Police said.
Neither the arrested man nor the alleged victim can be named.
Following the Panorama documentary, chief executive of Ofcom Dame Melanie Dawes said the allegations raised "really serious concerns" and added the regulator is prepared to tighten its guidance around reality shows if necessary.
Channel 4 launched a review into contributor welfare in April, shortly after being contacted by the BBC regarding the accusations featured in Panorama.
The broadcaster's chief executive Priya Dogra has said reports that the show had been cancelled were "wholly inaccurate" and "no decision has been made" regarding the broadcast of the next series.
Ms Dogra said, after watching the programme, she was "deeply sorry" for the distress caused to MAFS UK participants who alleged they were raped and sexually assaulted by their partners.
MPs on the Culture, Media and Sport Committee have written to Channel 4 and Ofcom about their response to allegations in the BBC documentary.
Committee chairwoman Dame Caroline Dinenage said the accusations were "horrifying", adding: "Both Channel 4 and Ofcom, as the broadcasting regulator, have urgent questions to answer."
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Billed as a "bold social experiment", MAFS sees single people agree to "marry" total strangers, after meeting for the first time at their mock weddings.
The "marriages" on the show are not legally binding but the couples go on a "honeymoon" and move in together after their weddings.
The UK version of the reality series, which has been running for 10 seasons, is one of Channel 4's biggest shows, with audience numbers often topping three million.
But, in May, the broadcaster pulled all episodes of the show from its streaming service just hours before the edition of Panorama was aired.
Channel 4 has not yet decided whether to go ahead with the latest season of the show, which has already been filmed.
The 76-year-old, who helped traffic tonnes of cocaine, fentanyl, methamphetamine and other drugs into the US, was arrested in 2024 after he said he was kidnapped in Mexico and flown to Texas.
He then pleaded guilty to drug trafficking charges in August last year, after prosecutors said they would not seek the death penalty.
Speaking through a Spanish-language interpreter at the time, he apologised "to everyone who has suffered or been affected by my actions".
US District Judge Brian Cogan handed down the sentence at a hearing in Brooklyn federal court on Monday.
Along with a life sentence, he also faces $15bn (£11.2bn) in financial penalties.
Prosecutors said that Zambada ordered torture and plotted murders as he and co-founder Joaquin 'El Chapo' Guzman - whose son Joaquin Guzman Lopez was arrested with Zambada - grew the Sinaloa cartel into the world's largest drug trafficking organisation.
Sky's chief correspondent Stuart Ramsay witnessed production at a fentanyl lab run by the Sinaloa cartel in 2023 - where he saw how gang members then transported the drug by boat to a "stash house" ready for shipment to the US.
Prosecutors: Zambada sent 'staggering' amounts of drugs
Prosecutors added in a sentencing memo that Zambada "was one of the most - if not the most - prolific and powerful narcotraffickers in the world", adding "it would be difficult to overstate the magnitude" of his crimes and the scale of the "corruption, violence, and other harm he spread".
Federal authorities said in 2023 that the cartel was sending "staggering" amounts of fentanyl to the US, where the opioid kills thousands every year.
In 2023, at least three people were killed in retaliatory violence that Zambada directed after a large cache of fentanyl pills, methamphetamine and cocaine was stolen from the cartel, prosecutors added.
Months before Zambada's arrest, prosecutors also said that he ordered the murder of his nephew Eliseo Imperial Castro, also known as 'Cheyo Antrax,' after learning that Castro was claiming to be collecting debts for Zambada and pocketing the money without his permission.
After his and Lopez's arrests in 2024, violent clashes broke out in Culiacan between factions of the Sinaloa cartel. At least 12 people were killed.
Cartel violence broke out in February
According to the Reuters news agency, Zambada's lawyer Frank Perez said in a 6 July court filing that his client was fully aware he would receive a life sentence when he decided to accept responsibility for his crimes.
Mr Perez asked Judge Cogan to recommend to the Bureau of Prisons that the elderly Zambada be placed in a facility where he would receive adequate medical care.
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It comes after violence broke out in February after the killing of 'El Mencho' Nemesio Ruben Oseguera Cervantes, the leader of the Jalisco New Generation Cartel.
The 59-year-old was originally from the western state of Michoacan and had been heavily involved in drug trafficking since the 1990s.
He previously spent almost three years in a US prison after being convicted in 1994 of conspiracy to distribute heroin by a court in California.
The ruling, which applies for 14 days, was handed down by a US district judge ahead of a hearing in August.
That is set to determine whether the $110bn (£81.4bn) deal should be paused pending the outcome of the lawsuit brought by the 12 states involved, led by California.
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They argue the merger - mainly aimed at creating a bigger rival to the likes of Netflix - would substantially weaken competition in the US market, driving up prices for consumers and costing jobs.
The opposition is particularly fierce in Hollywood. Movie industry interest groups claim the deal would threaten the very future of cinema as it would bring together two of its five major studios.
The UK government has also outlined concerns.
The companies control UK-based TV channels, including Channel 5, TNT Sports, Cartoon Network, Nickelodeon, and CNN International, as well as the Paramount+ and HBO Max streaming services.
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Neither Paramount or WBD were yet to comment on the US ruling, which was handed down at the Oakland federal court in California.
The state's attorney general, Rob Bonta, said in a statement: "This is a critical first win in our case to ensure this megamerger never sees the light of day.
"History tells the tale of what happens when a few people have great power over markets that are central to Americans' lives: fewer opportunities for more people, worse products and services for all people."
The lawsuit could take many months to reach a conclusion - something that will worry Paramount.
Under the terms of its deal, it is obliged to pay Warner Bros shareholders a 25 cents-per-share fee for each calendar day the merger is delayed beyond 30 September.
It amounts to a bill of around $7m a day.
The teenager attacked Vicki Williams at Milford Haven Comprehensive School in Pembrokeshire in February. He was 15 at the time and cannot be named for legal reasons.
A Swansea Crown Court jury reached a majority verdict of 11 to one to convict the boy of wounding with intent after just over four hours of deliberation, on Monday.
The court had previously heard that the pupil, now 16, deliberately stabbed Mrs Williams after asking the history teacher to check his schoolwork.
He had approached her desk on the afternoon of 5 February. Mrs Williams said "alarm bells" began to ring in her head when he shut the door to the classroom, saying it was cold.
The jury was told the student then pulled a large kitchen knife from his bag, striking her in the head. The court heard that a "violent struggle" ensued in which Mrs Williams tried to take the knife from him before he ran from the school.
Earlier in the trial the boy told the court Mrs Williams had seen him with the knife and "tried to grab it" from him. He said he "accidentally assaulted her" in the ensuing struggle.
The boy pleaded guilty to possessing a kitchen knife on the school grounds.
Mrs Williams went to hospital in Haverfordwest and was found to have a wound to her scalp, scratches on her back and minor cuts to her hands.
The teacher told the jury she believed she was dying after the incident, which the prosecution said was a "sustained attack" and would have continued had she not disarmed him.
Matthew Roberts KC, defending, previously suggested the student had brought the kitchen knife into school in order to "show off" to other boys.
He said: "There was no recorded history of conflict between (the student) and Vicki Williams.
"There is no evidence of any animosity or any ill feeling between them at all."
The jury was shown CCTV of the teenager leaving the school premises, before he went to his grandmother's home, telling her: "Something went in my head, nan."
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Christopher Rees KC, prosecuting, said in his closing speech last week: "He knows the truth about what he did, he just doesn't have, I'm afraid, the courage or the remorse to tell anyone about it.
"He brought the knife into school because he planned to attack the teacher.
"Why Vicki Williams? Well, she was, at quarter past three, a lone female teacher, she was an easy target."
The boy will be sentenced on 3 September.
Customers in Sussex, Surrey, Hampshire and Berkshire will be placed under temporary restrictions from Saturday.
Despite the ban not coming in for several more days, the water firm said the 2.4 million customers should "immediately" cut back any use of hosepipes.
People are being urged not to use hosepipes for any purpose, including on their gardens, cars, patios, boats or swimming pools.
The firm said it has seen a "decline in river levels" and needs to "protect some groundwater sources" after lower than average rainfall, hot weather and high demand for water.
It comes after South East Water brought in a ban for customers in Kent earlier this month, including Ashford, Canterbury, Faversham, Maidstone, Sevenoaks, Snodland, Tenterden and Tunbridge Wells.
Douglas Whitfield, water supply director at South East Water, said: "Our absolute priority has to be making sure there is always enough water for everyone's essential daily needs - drinking, cooking and hygiene.
"To safeguard our shared resource and help prevent any homes from facing a sudden loss of water, we sadly need to ask our communities to not use their hosepipes immediately."
Over the weekend, 7,000 customers of the water firm living around the Tunbridge Wells and Pembury areas faced supply issues.
Households experienced low pressure, intermittent supply or no water after an "instrument failure" caused a water treatment works to shut down, said South East Water.
Services were restored on Sunday evening, the firm added.
Last week, the industry watchdog said South East Water is facing a £30.5m redress package for multiple other customer service failures.
Areas affected by hosepipe bans
'Temperatures widely above average'
Forecasters said the UK will remain dry in the days ahead, while it is "uncertain" if rain in northern areas will reach southern parts.
Sky News meteorologist Dr Christopher England said: "The UK is going to be essentially dry into the weekend, with temperatures widely above average, although northern and western parts in particular will be fairly cloudy with a little drizzle and largely inconsequential rain.
"Saturday looks like bringing some locally heavy rain into the North West, which will spread southeast across England and Wales, but how far it will get before petering out is uncertain at this stage.
"Thereafter, it's all very uncertain for the first week of August, but likely warm with some rain in the North, while the South will be mainly dry."
'Longest unbroken spell of no recorded rain'
It comes as central and southeast England have seen the longest unbroken spell of no recorded rainfall this century, according to Met Office figures.
An average of zero rainfall has been measured across the organisation's weather stations in both regions for 14 days in a row, from 2 July to 15 July, according to latest data.
This is the longest unbroken run of days with no rain for southeast England since a 15-day spell in April 1997.
For central England, it is the longest period since a 14-day run of no recorded rainfall in June 1996.
Data for 16 July has yet to be published.
Reservoir storage levels in England are currently at 79%, around five percentage points below the long-term average for the time of year, the Environment Agency said.
Six reservoirs are classed as having "notably low" levels, including Wimbleball in Somerset, Grafham in Cambridgeshire and Hanningfield in Essex, while Blagdon reservoir in Somerset is classed as being "exceptionally low".
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It comes after there have been 28 days in 2026, consecutive and non-consecutive, when 30C has been exceeded somewhere in the UK - seven in May, eight in June and 13 in July.
The record for the number of 30C-plus days in a calendar year is 34, which was set in 1995.
A new report recently revealed the UK is experiencing a period of "historic and unprecedented change" to its climate.
Man-made climate change, mostly caused by burning fossil fuels, is driving more extreme weather - and in the South East, the hottest day of the year is 4.5C warmer on average than it was just a few decades ago, the Met Office said.