Investigators say the Cumbria rail crash, in which one woman died, could have been caused by a set of points.
The front of the train doubled back on the carriages
Margaret Masson, 84, of Glasgow, died and eight other people were seriously hurt when a Virgin train derailed at Grayrigg, near Kendal, at about 95mph.
Network Rail, which is responsible for maintaining track, said it was now checking points in the crash area.
Virgin boss Sir Richard Branson said the driver of the London to Glasgow service, Iain Black, was "a hero".
"He could have tried to get back and protect himself but he didn't and he has ended up quite badly injured," Sir Richard said.
Mr Black, 46, a former police officer from Scotland, suffered a serious neck injury.
Consultant Eymon Jundi, who is treating him at the Royal Preston Hospital, said he was in "very good spirits", but would probably spend "a week or 10 days" in hospital.
Police said 22 people, including Mrs Masson's daughter and son-in-law, Margaret and Richard Langley, went to hospital after the accident at 2015 GMT on Friday, while dozens more were "walking wounded".
Margaret Jones, 41, the granddaughter of Mrs Masson, from Cardonald in Glasgow, said she was devastated by her death.
British Transport Police said it was up to Network Rail and the train operators to decide when to reopen the line, but he warned it could take a week or more to complete the crash inquiry.
Muddy conditions underfoot and the need to build a temporary road to allow heavy-lifting gear on to the scene were proving "real challenges" to the investigation, he said.
Thomas Edwards, who is leading the Rail Accident Investigation Branch's inquiry, said he agreed with the police that the main focus of the investigation was a set of points.
Mr Edwards said: "We've been and inspected the train, the track and, in particular, we have been focussing our investigations on a set of points in a cutting."
Sir Richard arrived at the scene of the accident after returning from a holiday.
He said he had been told that points were to blame, and added it was a "sad day".
"Everyone is going to have to learn from this incident and Network Rail are going to have to look at this track problem and make sure nothing like this ever happens again," he said.
He also said the Pendolino was "built like a tank" and that the accident could have been much worse if it had involved an old train.
The chief executive of Network Rail, John Armitt, acknowledged that there might have been a points failure.
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He said: "A points failure can obviously be due to various causes, but clearly there is a possibility that it has been something which has occurred which Network Rail is responsible for, but at the moment I cannot say that."
He said the points were last serviced earlier this month, and that track maintenance was carried out by Network Rail employees, not a private contractor.
Chief Superintendent Martyn Ripley of British Transport Police said he was amazed there had not been more fatalities among the 100 passengers on board.
Bob Crow, general secretary of the Rail Maritime and Transport Union, said that if points failure was the cause there must be an investigation into any management failings.
One of the rail carriages was forced upright following the crash
He said the points concerned would only be used to switch traffic in an emergency or for engineering work and had not been operated since February 15.
The points would be operated locally and only after being given permission and released by senior staff.
The 22 passengers needing hospital treatment were taken to three hospitals, with the Royal Lancaster Infirmary and the Royal Preston Hospital admitting the most serious casualties.
Of the eight patients who were seriously injured, five are improving in hospital, while three remain in a serious condition.
Passengers suffered a mixture of head, back, neck, leg and some internal injuries.
Virgin Trains have suspended services between Lancaster and Lockerbie, with replacement buses operating. Trains are running as normal to and from Lockerbie, and between London and Lancaster.
Seven people died and 76 were injured when poorly maintained points derailed a train at Potters Bar, Hertfordshire in May 2002.
The Grayrigg accident happened seven miles (11 kilometres) from the scene of a disaster at Tebay in February 2004, where four railway workers were killed by a runaway wagon, also on the West Coast Main Line.
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