They said the ValuJet DC-9 appeared to have bored into the swamp "like a power drill" on Saturday and either disintegrated or was swallowed up by mud and quicksand.
The search for bodies and the flight recorders continued, using helicopters and "airboats", fan-driven swamp vessels which cut through sawgrass and reeds in the Everglades national park.
Lewis Jordan, president of the Atlanta-based ValuJet, denied that the 27-year-old aircraft had been too old, but admitted it had had a series of problems in recent months. Air safety officials said it had turned back to airports seven times in two years with technical problems.
Last night it was confirmed that two British citizens were among the 109 dead. The airline gave their names as Devlin Loughney and Roger Loughney. No addresses were given.
A passenger on board the same aeroplane earlier on Saturday said it appeared to have had problems before and during that flight.
ValuJet Flight 592 from Miami International Airport to Atlanta took off around 2pm on Saturday. After circling north-west, the pilot requested permission to return, reportedly citing smoke in the cockpit.
It then disappeared from traffic controllers' screens. A light aircraft pilot who saw it go down said it plunged into the swamp, about 20 miles north-west of the airport, "like a bullet".
Remains of Flight 592, page 3Reuse content