German police have rejected as speculation a report that a line controller turned off an automatic safety system shortly before two passenger trains collided in Bavaria.
Ten people were killed and scores more were injured, 18 seriously.
An unconfirmed report suggested that an automatic braking system had been switched off to allow one of the trains to make up time.
But a police spokesman rejected the theory as “pure speculation”.
“Discard that, we reject that,” a spokesman told local broadcaster Bayerischer Rundfunk.
The braking system, which is supposed to kick in when a train runs through a red light, was installed after a 2011 disaster at Magdeburg in which 10 people died.
Reports in German media suggested that in exceptional circumstances the automated system could be overridden by rail staff.
But police said the controller had been questioned on Tuesday as part of the inquiry and there was no immediate suspicion towards him. As the investigation was in its early stages, nothing could be ruled out.
Human error is still being investigated as a possible cause of the disaster, which happened on a single-track commuter line on Monday morning near Bad Aibling, a spa town about 60km (37 miles) south-east of Munich. The control room at Bad Aibling is also at the centre of the inquiry.
Transport Minister Alexander Dobrindt said the trains had crashed into each other while both were travelling at about 100km/h (62mph).
Although the search for a third data recorder is still being carried out, Mr Dobrindt told reporters on Wednesday that one of the “black boxes” had already been analysed. No technical fault or evidence of driver error had been found on the westbound train, he said.
But the eastbound train’s data recorder may be of more importance, as it was several minutes late when the two trains crashed head-on.
Nine of the 10 victims of the crash were men. Both train drivers and two train guards were among those killed.
The 10th victim was a teenaged girl, according local reports.
Police said that the search of the wreckage had been completed and no more victims had been found or were missing.
None of those being treated in hospital was in a life-threatening condition, they added.
The search has been complicated by the difficult terrain where the crash happened.
A 160-tonne crane arrived at the scene of the disaster on Wednesday, as salvage workers prepared to remove the two mangled trains from the track. The work was expected to last at least two days.
Bavarian State Premier Horst Seehofer laid a wreath at the site with his colleagues and said it was a tragedy. “The whole of Bavaria has been shaken,” he said.
The trains collided in a hilly and densely wooded region near the Mangfall river.
Investigators will have to find out why a train that left Holzkirchen travelling east to Rosenheim was on the single track at 06:48, four minutes after it was due to reach its next stop at Kolbermoor, where it would have met the westbound train on a double track.
The westbound train from Rosenheim to Holzkirchen would have left Kolbermoor at 06:45 and would have been expected to be on the single track at the time of the accident.
As the PZB automated braking system had been checked a week ago, there has been heightened speculation that it may have been temporarily disabled, and it is the controller’s responsibility to ensure trains are running safely.