Bad Aibling train crash tributes
Rescue workers stand by the wreaths placed in front of two crashed trains near Bad Aibling in southwestern GermanyREUTERS/Lukas Barth

A source close to the investigation into the train crash near Bad Aibling in Germany which killed 10 people and injured dozens more has said that a signal controller's actions are being scrutinised to determine whether it is linked to the disaster. Two trains collided head-on as they travelled in opposite directions on a single stretch of track which had remained open for both.

Around 100 people were injured in the crash, some seriously. Rescuers are still searching through the wreckage for one person, but have been hampered by the location of the crash, which occurred between a hillside and river. Both drivers and both conductors died in the collision, which took place as the two passenger trains went around a bend, leaving them with no time to brake before one slammed into the side of the other. Two of three black boxes have been recovered and Deutsche Bahn, which runs the track, is helping with the investigation.

Both trains are believed to be fitted with automatic braking mechanisms and mechanical failure is one line of enquiry. According to some German newspapers, a signaller may have disabled the automatic signalling mechanism, possibly because one train was running late. This would have prevented the braking systems being activated, leaving the second train to go ahead before the other could branch off.

A source who did not wish to be identified told Reuters that a signal controller was being scrutinised. "The investigations are focusing on the controller," the source said.

German Chancellor Angela Merkel said: "My sympathy goes out especially to the families of the nine people who have lost their lives." The accident was the worst on German railways since 1998 when 101 people died in a train crash in Eschede.