Sriwijaya Air’s flight crashed into waters off Jakarta on January 9, killing 62 passengers and crew, including nearly a dozen children.
A post-crash investigation shows Indonesian passenger jet’s throttles showed an “anomaly” and had been repaired several times before a deadly accident last month. Investigators on Wednesday said the exact cause of the crash was still unclear.
The 26-year-old plane passenger jet with 62 passengers and crew, including nearly a dozen children, were killed when the Sriwijaya Air Boeing 737-500 plunged around 10,000 feet (3,000 metres) and crashed into waters off Jakarta on January 9.
"The left (engine throttle) was moving backward too far while the right one was not moving at all -it was stuck," said National Transportation Safety Committee investigator Nurcahyo Utomo.
The agency on Wednesday released its preliminary report on the crash that killed all 62 passengers and crew.
"But what would have caused this anomaly? We can't conclude anything just yet."
Authorities have previously said the crew did not declare an emergency or report technical problems with the aircraft before its dive, and that it was probably intact when it hit the water.
They cited a relatively small area where the wreckage was scattered and details from a retrieved flight data recorder - one of two so-called "black boxes" - showing the engine was still running just before it crashed.
Communications with air traffic control were described as normal up until the moment that the plane sharply deviated from its intended course and crashed.
The crew, including an experienced captain, did not reply to questions about the plane's change of direction.
While the flight had been delayed due to bad weather, there was no indication that the conditions played a pivotal role in the accident, authorities said, adding that two other commercial planes flew the same route without incident just before and after the plane.
Maintenance logs pointed to a possible issue with the plane's auto throttle, which controls engine power, authorities have said, but it was not clear what role - if any - the potential malfunction played.
The auto throttle and several other components were being tested for signs of a problem.
Meanwhile, the hunt has continued for a still-missing cockpit voice recorder, which records flight crew conversations.
A team from the United States' National Transportation Safety Board is taking part in the investigation, along with staff from Boeing and the Federal Aviation Administration.
Sriwijaya Air, which flies to destinations in Indonesia and across Southeast Asia, has previously had safety incidents - including runway overruns - but no other fatal crashes since starting operations in 2003.