BEIRUT (Reuters) - Pilot error caused the crash of an Ethiopian Airlines plane off the coast of Lebanon last month which killed all 90 people on board, a source familiar with the investigation into the accident said Tuesday.

"The investigation team has reached an early conclusion that it was pilot error, based on the information from the black box," the source told Reuters.

An investigation team involving Lebanese, French and Ethiopian officials had headed to France Monday with the flight recorders, commonly known as "black boxes," for analysis.

The Boeing 737-800 plane crashed minutes after taking off from Beirut in stormy weather on January 25, plunging in a ball of fire into the sea.

The pilot had failed to respond to the control tower's request to change direction even though he acknowledged their demands. The plane made a sharp turn before disappearing off the radar, the Lebanese transport minister said at the time.

The eight-year-old plane, carrying mostly Lebanese and Ethiopian passengers, last had a maintenance check on December 25 and no technical problems had been found. It was bound for the Ethiopian capital Addis Ababa.

Since retrieving the flight recorders from the Mediterranean Sunday, Lebanese and international search teams have also located parts of the plane's fuselage, where most of the victims' bodies are believed trapped.

The bodies of at least 23 victims have been recovered so far.