A United Airlines flight had to turn around after one of the toilets started leaking into the cabin, report says

• A United Airlines flight turned around after a bathroom malfunction.
• Passengers reportedly said the toilets' contents overflowed into the cabin.
• United is facing increasing scrutiny from the FAA following a spate of malfunctions.

A transatlantic United Airlines flight was forced to turn around on Friday after one of its toilets malfunctioned and began leaking into the cabin, the German outlet RTL first reported.

The Boeing 777 was about an hour into the journey from Frankfurt, Germany, to San Francisco when it began circling over the North Sea, according to data from the flight tracker Flightradar24.

After doing a couple of loops over a stretch of water between the UK and the Netherlands, the United flight ended back where it started.

A United spokesperson told Business Insider that Flight UA59 had to make the U-turn due to "a maintenance issue with one of the aircraft's lavatories."

Passengers said the contents of the toilet overflowed into the cabin, RTL reported.

"We arranged for another plane to take customers to San Francisco the next day and provided them with hotel accommodations overnight in Frankfurt," the United spokesperson also told BI.

A flight on the same plane the following day was canceled, presumably as it had to undergo maintenance. The 777 returned to service on Sunday, Flightradar24 data shows.

This isn't the first time a transatlantic flight has had to turn around due to plumbing issues.

In February, a KLM Boeing 787 Dreamliner diverted after eight of its nine bathrooms stopped working, as Business Insider previously reported.

United has experienced a number of mechanical problems in recent weeks.

Last month, a Boeing 777 lost a tire shortly after taking off from San Francisco — crushing a car in the parking lot, CBS News Bay Area reported.

A week before this latest incident, the carrier's vice president of corporate safety told employees that regulators were increasing scrutiny of United.

Bloomberg reported that the Federal Aviation Administration (FAA) was blocking United from approving or promoting pilots to different plane models and that more drastic actions, such as preventing it from adding new flight routes, were also under consideration.