Rescuers at the scene of the Selby train accident can still hear mobile phones ringing from inside the mangled carriages.
Police officers described the ringing as "unnerving" and said it could be several days before the exact death toll from the disaster is known. The bodies of the 13 known victims have been recovered from the Yorkshire crash site.
Chief Insp Martin Hemingway said more bodies could still be in the parts of the wreckage which have not yet been searched. Bodies have been taken to a makeshift mortuary for identification.
Mr Hemingway said: "The high-speed collision caused tremendous damage and there are areas on two carriages and underneath some of the carriages we have not yet been able to search.
"It is possible more fatalities may be seen in these areas but we will not know that until heavy lifting equipment has been used to move the carriages."
Land Rover driver Mr Gary Hart (36), whose vehicle triggered the two-train collision when it careered off the M62 on to the track, was described by his stepfather Mr Martyn Taylor as being "inconsolable with grief".
Police said the possibility Mr Hart, from the village of Strubby, in Lincolnshire, fell asleep at the wheel was among aspects of the accident being looked at. Mr Hart's wife denied this was the case in a news conference, however.
East Coast train company GNER, whose Newcastle-London express was derailed after hitting the Land Rover and then wrecked in the collision with a coal-laden goods train travelling north on the neighbouring track, said three of its staff were unaccounted for.
By early this evening, 33 of the 70 people injured in the crash were still in hospital. Two were in a critical condition at Pinderfields Hospital in Wakefield, West Yorkshire.