Black Box Suggests Mechanical, Pilot Error to Blame for Russian Military Plane Crash Preliminary analysis suggests a combination of the two are to blame.

 -- The preliminary analysis of a black box from a Russian military plane that crashed Christmas Day suggests a combination of pilot error and mechanical error are to blame, according to Russian media.

The investigation into the crash has not yet revealed why the plane's wings experienced a problem with the flaps, the moveable panels mounted on the edge of the wings that increase lift, a source familiar with the investigation told news agency Interfax.

Another source aware of the details in the preliminary crash investigation told Interfax that although a mechanical error could be to blame, "The crew's erroneous actions during takeoff shouldn't be ruled out either."

The preliminary theory is that the pilots reacted incorrectly to the issue, and the plane crashed as a result, according to Interfax.

The plane had two black boxes, only one of which has been recovered so far.

The Tupolev Tu-154 aircraft crashed into the Black Sea on Sunday just two minutes after it departed in good weather from Sochi, killing 92 people aboard, including a famous choir, The Associated Press reported. The Red Army Choir was traveling to a New Year's concert at a Russian military base in Syria, according to The AP.

On Tuesday, thousands of rescue workers sped up efforts to recover bodies and wreckage from the crash site, ahead of forecasts of bad weather, The AP reported. Drones and submersibles are also being used in recovery efforts.

The top Russian investigative agency, known as the Investigative Committee, said it found a witness who filmed the crash, according to The AP. Details on the alleged video were not offered.

The Tu-154 is a Soviet-built airliner designed in the late 1960s. Russian airlines decommissioned the three-engine aircraft years ago, but the military and other government agencies continue to use it, The AP reported. The plane, although gas-guzzling and noisy, is loved by crews for its maneuverability and sturdiness, according to The AP.

ABC News' Ben Gittleson and Anastasia Butler contributed to this report.