Railtrack's chief executive Gerald Corbett has offered his resignation following the Hatfield train crash.
His move came after it emerged a broken rail could be responsible for the derailment which claimed four lives and injured 35 others.
Meanwhile, British Transport Police revealed that there might still be more bodies beneath the mangled carriages.
Four men, all believed to have been in the buffet car, are so far known to have died and 35 people were injured, including a Harrogate woman, when the train derailed at 115 mph on a bend in Herts.
A transport police spokesman said: "We cannot rule out the possibility there may be more bodies until we have lifted the carriages. But we cannot do that until investigators have finished their finger-tip search of the area."
Passengers from York were facing lengthy delays today after Railtrack imposed blanket speed restrictions on 14 curving sections of the East Coast Line similar to the track at Hatfield. The limits have all been reduced by a third.
York-based GNER said it was operating a revised timetable on the route from York to Kings Cross with journeys diverted via Hertford and likely to take about an hour longer than normal.
And about dozen services up and down the line from York were cancelled altogether.
Passengers at York railway station were today trying to cope with the delays and cancellations.
Vicky McIver and Susan Thurlow, from Pocklington, who were both trying to get to a business meeting in Croydon, said the train they were waiting for was already 20 minutes late and they had been told to expect the journey itself to be at least half an hour longer than usual.
Vicky said she was not worried about rail travel. "I use this rail line a lot and I have never had any problems before, apart from a couple of bomb scares. Usually it's a good service," sahe said.
For travel advice contact 08457-225225 or 08457-484950.
The casualty bureau number is 0845-944-1551.
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