Passengers on an American Airlines flight that landed at Denver airport Thursday evening were forced to evacuate onto the wing of the plane when an aircraft engine caught fire.

Dozens of passengers could be seen crammed onto the wing as clouds of white, then thick black smoke began enveloping the plane.

The fire was extinguished and all passengers were evacuated, an airport spokesperson told CNN. Twelve passengers were taken to the hospital with minor injuries, according to the Denver Fire Department.

There were 172 passengers and six crew members aboard,

The engine caught fire as the American Airlines Flight 1006 was taxiing down the runway in Denver.

The Boeing 737-800 aircraft had been headed from Colorado Springs to Dallas-Fort Worth from Colorado Springs, but was diverted to Denver at 5:15 p.m. when the crew reported “engine vibrations,” according to a statement from the Federal Aviation Administration.

“After landing and while taxiing to the gate an engine caught fire,” the statement said.

An FAA investigation is ongoing.

The pilot notified air traffic controllers in Denver that the plane was experiencing engine issues, but that it was not an emergency, according to air traffic control audio.

“American 10,006, uh, 1006 just to verify not an emergency still, correct?” the controller asked in audio captured on LiveATC.net.

“Nah, we just have a high engine vibration so we are cruising slower than normal,” the pilot said.

But several minutes later after the plane landed, someone on the radio yelled “Mayday, Mayday, Mayday! Mayday! Engine fire!”

American Airlines issued a statement thanking “our crew members, DEN [Denver] team and first responders for their quick and decisive action with the safety of everyone on board and on the ground as the priority.”