A train driver killed in a crash acknowledged a red signal but continued to speed up as he passed it, according to investigators.
Shaun Burton, 60, died when his train hit the back of a stationary one near Elstow, Bedfordshire.
More than 160 passengers were injured and 102 needed hospital treatment after both trains left the tracks.
The Rail Accident Investigation Branch (RAIB) said it was still looking for factors that could have influenced Mr Burton's actions.
Data recorders on the East Midlands Railway (EMR) train showed it acknowledged a red signal and passed it at about 58mph.
However, it "continued to accelerate, reaching a maximum speed of 76mph", according to an interim report.
Mr Burton applied the brake about 10 seconds before the crash and the emergency brake just two seconds later when the train was 200m away from impact, the RAIB said.
It was still travelling about 50mph at the time of the impact, according to the report.
Investigators said the stationary train - a service from Nottingham to London St Pancras - had stopped unexpectedly after a fault with its automatic warning system triggered the brakes.
It was this incident that automatically turned on the red signal on the track behind.
The RAIB said it was possible a curve just before the scene of the crash could have limited Mr Burton's view of whether the trains were on the same line.
It stressed its investigation into the 19 June incident was still in its early stages and "may contain information about immediate events without necessarily providing an explanation as to why they occurred".
"The reasons why train 1H46 passed signal WH154 at danger continue to form part of the ongoing investigation," the RAIB added.
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Operating company EMR said it was too early to draw definitive conclusions.
"We will continue to co-operate fully with RAIB while carefully considering the findings and any lessons that emerge from the investigation process," a spokesperson said.
"Our focus remains on supporting those affected by the incident, while continuing to work with the relevant authorities and carefully considering any recommendations identified through the investigation process."
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