A passenger train crashed head-on into another train in northwestern Turkey on Sunday, killing one of the engine drivers and injuring 14 other people, an official said.
The train went through a signal where it should have halted and slammed into another train that was stopped on the line.
There were conflicting reports as to what caused the accident.
The governor of Bilecik, some 250 miles (400 kilometers) south of Istanbul initially said the accident was caused by an electrical fault that led to signal failure.
But Hasan Gedikli, head of the railway system for the region, said the signaling system seemed to be functioning and that authorities were investigating why the train failed to stop.
One driver was killed _ it was unclear which one. The injured included two rail personnel, said Bilecik's governor, Musa Colak.
The trains were traveling in opposite directions between Istanbul and the city of Eskisehir.
Television footage from the crash site showed paramedics performing heart massage on a man lying on a stretcher beside the tracks.
Turkey's government has been working to improve the country's rail system, which is beset by signaling malfunctions, ill-equipped trains, deteriorating tracks and a lack of barriers at road crossings.
In Turkey's worst train accident in recent years, a newly inaugurated high-speed train from Istanbul to Ankara derailed in 2004, killing 37 people and injuring 95 others.