Black box data from the TransAsia Airlines turbo-prop plane that crashed in Taiwan has revealed that power was cut to both engines, investigators say.
Taiwan's Aviation Safety Council said the engines failed to produce enough thrust for two minutes after take-off.
Data suggest that the flight crew tried to stop and restart one of the engines, without success.
Flight GE235 carried 58 passengers and crew, at least 35 of whom died when the plane crashed into a river.
Fifteen people survived the crash.
According to investigators at a briefing in Taipei, the plane ran into trouble just 37 seconds after taking off from Taipei's Songshan airport.
Dramatic dashcam images show the TransAsia passenger plane clipping a bridge as it plunges towards the river
Thomas Wang, director of the Aviation Safety Council, said the pilot announced a "flame-out", which can occur when the fuel supply to the engine is interrupted or when there is faulty combustion.
However, Mr Wang said there was in fact no flame-out, and the right-hand engine had actually shifted into idle mode without the oil pressure having changed.
"The plane flashed a flame-out signal for one of the two engines at 10:53:28 when the plane climbed to an altitude of 1,200ft, triggering a warning," AFP news agency quoted Mr Wang as saying.
"Then the other [left] engine was shut down manually. The pilot tried to restart the engines but to no avail.
"That means that during the flight's final moments, neither engine had any thrust. We heard 'Mayday' at 10:54:35," he added.
The flight, which had been bound for Taiwan's Kinmen Island, crashed into the Keelung River just 72 seconds later.
The plane, an ATR 72-600, is able to fly with just one functioning engine. Mr Wang said it was not clear why the left engine had been shut down.
A more substantial report into the crash will be released within the next 30 days, ahead of the publication of a final report in the next three to six months.
The pilot, Liao Chien-tsung, has been praised by Taipei's mayor for managing to steer the plane away from apartment blocks and commercial buildings before it came down.
Taiwanese Vice President Wu Den-yih also paid tribute the 42-year-old pilot, saying he had "meticulously grasped" the flight controls in the plane's last few seconds in the air, according to the Associated Press news agency.
"In the final moments he still wanted to control the plane to avoid harming residents in the housing communities," he was quoted as saying.
Aviation authorities have ordered checks on all remaining ATR aircraft being used by Taiwanese companies
Rescue and retrieval teams say poor visibility in the river has hampered the search operation
Crash investigators told Taiwanese media that Mr Liao's hands were still on the plane's controls when his body was found, Reuters reported.
Both the pilot and co-pilot were found dead in the cockpit with their legs badly broken, according to local media reports.
Taiwan's aviation regulator has ordered thorough engine and fuel system checks on the remaining 22 ATR-manufactured aircraft currently in active service on the island.
The BBC's Cindy Sui in Taipei said search and rescue teams had been focussing their efforts downstream of the crash site, and are carrying out operations along a 15-kilometre (9-mile) stretch of the river.
The main parts of the plane, which had been submerged, have been retrieved from the water, and divers are now attempting to locate the bodies of other victims.
Search officials said on Thursday that it was extremely unlikely that any additional survivors would be found, and said that retrieval efforts had been severely hampered by poor visibility in the murky water.