Investigators looking into the Sriwijaya Air crash in Indonesia say they are now focusing on the plane's autothrottle.
Sixty-two people were on board the passenger plane when it plunged into the sea minutes after taking off from Jakarta on 9 January.
A few days before the crash, a problem with the Boeing 737's autothrottle had been reported, officials said.
The autothrottle controls the engine power of an aircraft.
Usually pilots can also control the throttle manually and it remains unclear whether it is in fact was the cause of the crash.
"There was a report of malfunction on the autothrottle a couple of days before to the technician in the maintenance log, but we do not know what kind of problem," National Transportation Safety Committee (KNKT) investigator Nurcayho Utomo told news agency Reuters.
"If we find the CVR (cockpit voice recorder) we can hear the discussion between the pilots, what they talked about and we will know what is the problem."
So far only the aircraft's flight data recorder has been recovered from the debris in the Java Sea. Divers are still searching for the cockpit voice recorder.
A preliminary report is expected within 30 days of the crash, in line with international standards.
The airline itself said it would not comment on the investigation before the official statement.
What's known about the crash?
The Sriwijaya Air passenger plane departed from Jakarta's main airport at 14:36 local time (07:36 GMT) on 9 January. Flight SJ182 was en route to the city of Pontianak on Borneo island.
Minutes later, at 14:40, the last contact was recorded.
There were 50 passengers - including seven children and three babies - and 12 crew on board, though the plane has a capacity of 130. Everyone on board was Indonesian, officials say.
Witnesses said they had seen and heard at least one explosion. A damaged fan blade found by the divers suggested the plane was still functioning when it hit the sea, and did not explode mid-air.
The 26-year-old Boeing 737 passed an airworthiness inspection in December 2020 after it had been grounded for some time during the pandemic.
Sriwijaya Air, founded in 2003, is a local budget airline which flies to Indonesian and other South-east Asian destinations.