One of the engines on TransAsia Airways Flight 235 went idle 37 seconds after take-off, Taiwan's top aviation safety official has said.
Aviation Safety Council executive director Thomas Wang also said the pilots may have shut off the remaining engine before attempting to restart both, but the plane crashed before that could happen.
Mr Wang presented the preliminary findings from the flight data recorder at a news conference in Taipei.
Wednesday's crash minutes after take-off killed at least 35 people and left eight missing.
Fifteen people were rescued with injuries after the accident, which was captured in a dramatic dashboard camera video that showed the plane banking steeply and scraping a highway overpass before it hurtled into the Keelung River in the capital.
Mr Wang said the plane's right engine triggered an alarm 37 seconds after take-off. However, he said the data showed it had not shut down, or "flamed out" as the pilot told the control tower, but rather moved into idle mode, with no change in the oil pressure.
Then, 46 seconds later, the left engine was shut down, apparently by one of the pilots, so that neither engine was producing any power. A re-start was attempted, but the plane crashed just 72 seconds later.
Mr Wang said it was too early to draw firm conclusions about the reasons why the engines ceased producing power.
"It's only the third day so we can't say too much," he said. "We haven't ruled anything out."
Taiwanese Vice President Wu Den-yih, mindful of the island's reputation as a tourist destination and its tense relations with China where most of the flight's passengers were from, attended a prayer session at a Taipei funeral parlour to pay respects.
At the parlour, where bodies are being stored, Mr Wu expressed condolences and praised pilot Liao Chien-chung, who died in the crash. The pilots may have deliberately steered the plane away from buildings and into the river in the final moments.
"When it came to when it was clear his life would end, (the pilot) meticulously grasped the flight operating system and in the final moments he still wanted to control the plane to avoid harming residents in the housing communities," Mr Wu said.
"To the plane's crew, the victims ... I here express condolences."
Divers from a local fire agency found one female and three male bodies in the mud at the bottom of the river about 50 yards (meters) from the crash site, a Taipei City Fire Department official said.
The agency suspects the eight bodies that are still missing may be in equally murky areas and has sent 190 divers to look for them.
Taiwan's Ministry of National Defence dispatched three S-70C rescue helicopters to search along a river system that runs into the ocean off Taiwan's north-west coast.
More than 30 relatives of victims cried wildly, prayed or were comforted by Buddhist volunteers at the riverside as divers in black wetsuits brought back the four bodies. Some divers came ashore with their hands joined in prayer for the people they brought back.
The bodies of the pilot and co-pilot were found earlier with their hands still on the controls, Taiwan's ETtoday online news service said.
Mr Wang said the cockpit flight recorder was still being analysed and a transcript would be provided as soon as possible.
Investigators are to issue a preliminary report on the crash within 30 days and a fuller report within three-four months. A final draft will be submitted within eight months and the full investigation concluded in about a year, Mr Wang added.
He said the engines had shown no problems before the flight and repeatedly stated that the plane would have been able to take off and fly even with only one engine working.
Earl Chapman, of Canada's Transportation Safety Bureau, told the news conference that the plane's Pratt & Whitney engines were known for their reliability.
"This engine type has millions of flight hours behind it with a very good safety record. So it's fairly unremarkable in that respect," said Mr Chapman, who was participating in the investigation because the engines were made by Pratt & Whitney's Canadian division.
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