Divers off the Indonesian coast recovered the flight recorder from the doomed AirAsia jet on Monday and tried to dislodge a second data-filled device from the wreckage of the plane, which went down last month with 162 people aboard.

The discoveries marked a critical step for investigators seeking to piece together the reason for the Dec. 28 crash.

The plane disappeared minutes after the pilot asked for permission to climb to a higher altitude in an apparent attempt to bypass rough weather while en route to Singapore.

Weeks of heavy rain and storm-tossed seas have hindered attempts to recovery bodies and probe the wreckage of the Airbus A320-200, resting in about 100 feet of water in the Java Sea.

On Saturday, crews using balloons raised a portion of the tail section, where the flight recorders — the so-called “black boxes” — are located. But the devices had been torn from their sites.

The flight data recorder was found beneath a piece of the plane’s wing. The other device, the cockpit voice recorder, remained pinned under heavy wreckage, said Suryadi Bambang Supriyadi, operations coordinator for Indonesia’s national search and rescue agency.

The flight data recorder will be analyzed in Jakarta. Officials said it could be as long as two weeks to fully download and analyze the information.

Previous review of radar tracking information led some experts to theorize the plane could have stalled during a steep climb.

A total of 48 bodies have been recovered, but investigators believe many remain trapped amid the sunken wreckage.