The engine of an American Airlines plane caught fire at the Denver Airport on Thursday evening, forcing passengers to evacuate onto the wing of the plane.

Two investigators from the National Transportation Safety Board were already at work Friday to look into the fire that appeared after American Airlines flight 1006 arrived in Denver the evening before.

A fire on an American Airlines plane after it diverted mid-flight and landed at Denver International Airport sent passengers fleeing onto a wing in a fraught evacuation amid billowing clouds of smoke.