Airport spokesman Perry Cooper said the incident involving the Boeing 777 jet was not caused by a birdstrike.
Asiana Flight 271 took off on April 29 bound for Seoul, South Korea with 179 passengers and 16 crew on board. Several witnesses on the ground near the airport said as the plane was ascending, they heard several loud explosions and flames shooting out of the left engine.
The plane dumped fuel over Puget Sound before landing without incident at about 3:30 p.m. and taxiing to the gate.
No one was injured and there were no major delays for other flights.