By Bernadette Christina Munthe and Agustinus Beo Da Costa

JAKARTA (Reuters) – Indonesian divers resumed a search on Thursday for the remains of 62 victims and the cockpit voice recorder from a Sriwijaya Air plane that plunged into the Java Sea soon after takeoff last weekend, officials said.

The search at the crash site of the Boeing 737-500, which was traveling from Jakarta to Pontianak, had been temporarily suspended on Wednesday after bad weather whipped up high waves.

A team of divers recovered one of the plane’s black boxes, the flight data recorder (FDR), from the seabed earlier this week and efforts were underway on Thursday to retrieve the cockpit voice recorder (CVR).

With the cause of the fatal crash of the nearly 27-year-old plane unclear, investigators will rely heavily on the black boxes to determine what caused it to lose control minutes after take-off.

Indonesia National Transportation Safety Committee (KNKT) head Soerjanto Tjahjono told Reuters the FDR information was still being processed and a preliminary report would be published within 30 days of the crash in line with international standards.

Tempo newspaper on Thursday reported the plane had experienced recurring problems with the autothrottle system that automatically controls the engine power settings since returning from storage last month. Sriwijaya did not respond immediately to a request for comment.

Tjahjono said if the autothrottle system was not working, the pilots could control the settings manually with their hands.

An airline pilot who was not authorized to speak publicly said it was considered acceptable for a plane to fly when the autothrottle system was not working, though it would increase the pilot workload and could prove distracting in an emergency situation.

Most air accidents are typically caused by a range of factors that can take months to establish, according to safety experts.

The Sriwijaya crash is the biggest airline disaster in Indonesia since 189 people were killed onboard a Lion Air Boeing 737 MAX that plunged into the Java Sea minutes after take-off in 2018.

(Additional reporting by Stanley Widianto in Jakarta and Jamie Freed in Sydney; Writing by Kate Lamb and Jamie Freed, Editing by Angus MacSwan)