Mechanical failure caused an engine fire that led to passengers and crew evacuating an Air China Ltd. flight via safety chutes at Singapore’s Changi Airport Sunday, according to a preliminary investigation, the airline said.

A more detailed investigation into the incident on the Airbus SE A320neo aircraft is underway, the Chinese carrier said in a statement.

All 146 passengers and nine crew members were safely evacuated after landing at about 4:15 p.m. Singapore time, and the fire in the left engine was extinguished 10 minutes later, according to a statement by the Civil Aviation Authority of Singapore. Nine passengers sustained minor injuries related to smoke inhalation and abrasions during evacuation, it said.

Videos circulated on social media showed flames visible in the rear of the left engine as passengers exited the plane on to the runway via escape chutes. Thick smoke filled the cabin, the videos show.

Air China Flight 403 reported smoke in the forward cargo hold and lavatory, declared an emergency and requested priority landing, the aviation authority said. The flight, which started from Chengdu in western China, was powered by RTX Corp.’s Pratt & Whitney engines. The plane is four years old, according to FlightRadar24 data.

RTX said in July that some 1,200 engines installed in Airbus SE A320-family narrowbody planes over a five-year period will need to be removed and inspected due to a “rare condition in powder metal” used in some parts.

Read More: Airlines Are Rankled About Pratt & Whitney’s Jet Engine Problems

After that disclosure, Hu Zhenjiang, deputy director of the Civil Aviation Administration of China, told Pratt & Whitney’s commercial engine president Rick Deurloo in a meeting in August that the company should continue to improve its production quality management and strengthen communication with Chinese airlines.

Pratt & Whitney didn’t respond to requests for comment.

Air China, which has 83 A320neo family aircraft built between 2015 and 2021, is one of the largest operators in Asia that face early engine removals, Bloomberg Intelligence analyst Tim Bacchus wrote in a note.

Singapore’s Transport Safety Investigation Bureau is investigating the incident and has contacted its Chinese counterpart, which will assist with the investigation, the aviation authority said. Changi Airport’s Runway 3 was closed for three hours, it said.