The National Transportation Safety Board said Wednesday that people did not begin fleeing the aircraft until 90 seconds later when a fire erupted.
Officials say the delay occurred as the pilot checked with the tower at the airport.
In addition, investigators said three flight attendants were flung from the plane during the landing. All three survived.
They had said Tuesday that two attendants were flung from the aircraft.
Two passengers were killed and many others were injured in the crash on Saturday.