A United Airlines flight bound for Japan experienced an engine malfunction after takeoff on Monday and returned to San Francisco International Airport, where it landed safely, airline and federal aviation officials said.

No injuries were reported from the incident involving United Flight 837, which ended when the four-engine Boeing 747 aircraft touched down without further incident shortly before 1:45 p.m. (21:45 GMT).

A United Airlines ual spokeswoman, Erin Benson, said the plane was carrying 202 passengers and 15 crew members en route to Narita International Airport on Tokyo. The Federal Aviation Administration initially reported that 231 people were aboard the jet.

The landing was described as “normal” in radio communications between the flight crew and air traffic controllers, as monitored on specialist website liveatc.net.

Shortly after the landing, the pilot contacted ground controllers to explain the trouble.

“We need the fire department to take a look at our No. 2 engine because it had an indication of compressor stall and possibly some paint that came out during the compressor stall,” the pilot was heard saying.

Benson also cited a stalled compressor in one of the engines as the reason for the plane’s return to San Francisco, adding that the airline could not confirm media reports of smoke or fire from the incident.

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She also said the pilot did not declare an emergency and that the landing followed about two hours of total flight time, including steps the crew took to dump excess jet fuel as a precaution before touchdown.

The flight-tracking website flightradar24 shows the plane flew several lengthy circuits just off the Pacific Coast west and south of San Francisco before returning to the airport to land – a sign that the trouble started soon after takeoff.

FAA spokesman Ian Gregor said the problem occurred with the “inboard engine on the left side” of the plane. He gave no further details.

A compressor stall is a sudden disruption to the core of an engine caused by abnormal airflow. It can be caused by a collision with birds or by unusual weather, according to aviation experts.

Local ABC News affiliate KGO-TV reported that one of the engines had caught fire and was shut down soon after takeoff. Live television coverage of the plane’s landing showed no sign of smoke or flames.

The 747-400 aircraft involved was manufactured and equipped with four Pratt & Whitney engines in 1999, according to FAA records, but it was not clear whether the original engines were still on the plane. Pratt was not immediately available to comment.