BERLIN (AP) — Emergency workers are working with two huge cranes to remove the wreckage of a head-on train crash that killed 10 people and injured dozens in southern Germany.

A spokesman for German Railways said the cleanup efforts in Bad Aibling started Thursday at daybreak. The cranes, equipped with railway wheels, were positioned at both ends of the crashed trains to remove debris.

The spokesman, who didn't give his name in accordance with company policy, said it wasn't clear how long the cleanup would take.

Authorities are trying to determine why multiple safety measures failed on Tuesday, allowing two trains to travel on the same single-line track and smash into each other. Investigators are considering possible technical errors, human failure or a combination of the two scenarios.