An engine aboard an American Airlines jet caught fire during a flight to Chicago on Sep. 28, forcing the pilots to return to St. Louis and evacuate the aircraft on the runway.

There were no reports of injuries aboard the MD-80 jet, said Jeff Lea, spokesman for Lambert Airport.

All 137 passengers, two pilots and three flight attendants left the plane safely after it turned back to Lambert and landed, said Tim Wagner, spokesman for Fort Worth, Texas-based American Airlines.

Flight 1400 reported engine problems sometime after takeoff and landed at 1:40pm CDT (18:40 GMT). Passengers walked down a staircase to the runway after emergency crews extinguished the fire with flame-retardant foam.

American Airlines maintenance will look at the aircraft and try to determine what caused the fire, Wagner said. The National Transportation Safety Board may get involved, he said.

The National Transportation Safety Board is sending at least two investigators, including a jet engine specialist, agency spokesman Peter Knudson said.