A signals control officer at the centre of a fatal train crash in Germany two months ago was allegedly playing a game on his phone at the time of the collision.
The man was taken into custody overnight accused of negligent homicide, over the crash which killed 11 people in southern Germany.
Prosecutors in the southern German town of Traunstein said they had issued an arrest warrant against the 39-year-old dispatcher, dpa has reported.
His name has not been revealed.
The fatal crash involved two trains colliding head-on, on a single line track near Bad Aibling, Bavaria in early February.
It is one of the worst rail accidents in German history.
Of the 11 dead, four were the train drivers, and seven were passengers. Eighty-five people were injured.
The man confessed that at the time of collision he was playing a game on his smartphone, Chief Public Prosecutor Wolfgang Giese said.
Investigators say it was not just a momentary lapse, but a more serious charge of breach of duty on the part of the signal officer.
The investigation into the cause of the disaster is continuing.