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This screen grab taken from video provided courtesy of TVBS Taiwan on February 4, 2015 shows a TransAsia ATR 72-600 turboprop plane clipping an elevated motorway and hitting a taxi (C) before crashing into the Keelung river outside Taiwan's capital Taipei in New Taipei City. The low-flying passenger plane, TransAsia Flight GE235 with 58 people on board, clipped the bridge and plunged into the river outside Taiwan's capital with at least 11 feared dead and many trapped inside.
TVBS Taiwan/AFP/Getty Images
This screen grab taken from video provided courtesy of TVBS Taiwan on February 4, 2015 shows a TransAsia ATR 72-600 turboprop plane clipping an elevated motorway and hitting a taxi (C) before crashing into the Keelung river outside Taiwan's capital Taipei in New Taipei City. The low-flying passenger plane, TransAsia Flight GE235 with 58 people on board, clipped the bridge and plunged into the river outside Taiwan's capital with at least 11 feared dead and many trapped inside.
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TAIWAN OUT
This screen grab taken from video provided courtesy of TVBS Taiwan on February 4, 2015 shows a TransAsia ATR 72-600 turboprop plane clipping an elevated motorway and hitting a taxi (C) before crashing into the Keelung river outside Taiwan's capital Taipei in New Taipei City. The low-flying passenger plane, TransAsia Flight GE235 with 58 people on board, clipped the bridge and plunged into the river outside Taiwan's capital with at least 11 feared dead and many trapped inside.    TAIWAN OUT  -- AFP PHOTO / TVBS Taiwan
---EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / TVBS Taiwan" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVESTVBS Taiwan/AFP/Getty Images
TVBS Taiwan/AFP/Getty Images
TOPSHOTS TAIWAN OUT This screen grab taken from video provided courtesy of TVBS Taiwan on February 4, 2015 shows a TransAsia ATR 72-600 turboprop plane clipping an elevated motorway and hitting a taxi (C) before crashing into the Keelung river outside Taiwan's capital Taipei in New Taipei City. The low-flying passenger plane, TransAsia Flight GE235 with 58 people on board, clipped the bridge and plunged into the river outside Taiwan's capital with at least 11 feared dead and many trapped inside. TAIWAN OUT -- AFP PHOTO / TVBS Taiwan ---EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / TVBS Taiwan" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVESTVBS Taiwan/AFP/Getty Images
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Story highlights

NEW: A TransAsia representative: Pilots who fly ATR planes must pass tests

The two engines stopped producing power, one after the other, aviation agency says

Official: Engine may have shut off due to a crew member or a mechanical issue

(CNN) —  

The death toll from a TransAsia Airways plane crash in Taiwan rose to 40 on Saturday, authorities said, as details emerged that both engines lost power.

The two engines on the ATR 72 turboprop aircraft stopped producing power one after the other, leaving the plane flying without thrust for more than a minute, according to the agency.

During the crisis in the cockpit, the pilots received a series of alerts, starting with an alarm related to one of the engines and followed by five stall warnings as the plane lost thrust..

The pilots issued a mayday alert to air traffic control, announcing an engine flameout, or power failure. They eventually managed to restart the engine, but it was too late to prevent a crash.

The Aviation Safety Council said Friday it was still collecting information on the disaster, with a full analysis of Flight GE235’s flight data recorder and cockpit voice recorder still months away, and wasn’t yet able to say why the engines shut down.

Thomas Wang, the council’s managing director, said investigators will look into the crew’s role, including the possibility they shut off the left engine in response to a warning about the right engine. He said the left engine could have stopped working for multiple reasons.

“Either someone reduced it or something else happened, a mechanical failure,” Wang said. “We don’t know.”

Eight people still missing

Flight GE235 crashed into the Keelung River in Taiwan’s capital, Taipei, shortly after taking off Wednesday with 58 people on board.

Authorities say that so far, 35 people have been confirmed dead, 15 survived and 8 are still missing, according to Taiwan’s official news agency CNA. Two people on the ground were also hurt.

Father’s hunch helped save toddler, wife

The reported engine problems dovetail with the account of Huang Chin-shun, a 72-year-old survivor of the crash.

“I thought something’s wrong with the engine because I always take this flight,” Huang told CNN affiliate ETTV from his hospital bed Thursday.

Stephen Fredrick, a pilot who once flew ATRs for American Airlines, told CNN this week that it looked like Flight GE235 was gliding when dashboard cameras on the ground captured the moments before it crashed into the river.

Fredrick pointed to the position of the nose, slightly down, and the wings, level. He said he thought the plane may have lost power in one or both of the engines.

TransAsia was involved in another deadly disaster in July. Forty-eight people died after an ATR 72 aircraft operated by the airline crashed as it was attempting to land in the Taiwanese Penghu Islands during bad weather.

After Wednesday’s crash, Taiwan’s aviation authorities ordered special checks on all ATR 72s in the fleets of local carriers.

And on Friday, TransAsia ordered its 71 pilots who helm ATR aircraft to take and pass written and oral exams within the next four days in order to fly again, said an airline representative, who was not named per custom. Those pilots will have to undergo flight simulator tests sometime in the future as well.

CNN’s David Molko, Mitra Mobasherat and Greg Botelho, plus journalists Annie Liao and Gladys Tse contributed to this report.