A preliminary report on last month's deadly crash of an Indonesian passenger jet was due to be released Wednesday, as the hunt continued for the plane's still-missing cockpit voice recorder.

All 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 26-year-old plane -- previously flown by US-based Continental Airlines and United Airlines -- came down just four minutes after setting off from the Indonesian capital.

Indonesian transport safety regulators are due to publish their initial report around 2:00 pm local time (0700 GMT).

Relatives of the victims have reportedly been briefed on its findings.

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.

Sriwijaya Air flight SJ182 came down just four minutes after setting off from Jakarta last month
Sriwijaya Air flight SJ182 came down just four minutes after setting off from Jakarta last month AFP / Azwar Ipank

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 autothrottle, which controls engine power, authorities have said, but it was not clear what role -- if any -- the potential malfunction played.

The autothrottle 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.

Indonesia, an archipelago that relies heavily on air transport to connect its thousands of islands, has suffered a string of deadly plane crashes in recent years.

In October 2018, 189 people were killed when a Boeing 737 MAX jet from Lion Air plunged into the sea.

That accident -- and another in Ethiopia -- led to the worldwide grounding of the 737 MAX over a faulty anti-stall system.

The 737 that crashed last month was not a MAX variant.