South Korean officials warned against prejudging the outcome of the investigation into the crash landing of an Asiana Airlines Boeing 777 at San Francisco International Airport over the weekend after it emerged that the pilot at the controls was still training to fly the aircraft.

Two Chinese teenagers were killed in the accident, according to officials at Asiana, one of South Korea’s two airlines. A further 289 passengers and 16 crew members escaped the aircraft before a fire devastated the fuselage. Six of the passengers were reported on Sunday as being in a critical condition.

The initial focus is on the crew’s handling of the landing in the final moments of the aircraft’s approach, after the Asiana flight from Seoul hit the ground short of the runway at San Francisco shortly before midday on Saturday.