Thousands of rail passengers on the East Coast Main Line are facing major delays due to overhead wire problems.
Operator East Coast said no trains were running between Grantham, Lincolnshire, and Peterborough, Cambridgeshire, because four power lines were down.
A limited service, with diesel trains, is expected to resume later on two of the four affected lines.
Services in both directions on the main line, between London King's Cross and Aberdeen, are affected.
East Coast said 70 of its 102 scheduled services were disrupted.
Earlier the company said delays were estimated at two hours and advised against travel that was not "absolutely necessary".
Shuttle services are running between King's Cross and Peterborough, and between Grantham and destinations north.
Passengers travelling from London can also use alternative services from St Pancras or Euston, where crowds of people have been trying to board trains.
Other train operators will accept tickets from customers affected, including on Sunday services, said government-run East Coast.
Network Rail will work overnight to fix the damage to the overhead power cables, with the aim of allowing timetabled services to run from Sunday morning.
A spokesman said it would be "all hands on deck" overnight to fix the damage in time for Sunday morning's timetable, adding: "A few of the very early morning services may be affected but we are expecting to be back to a full timetable by around 9am."
Passenger Lucy Bannister, travelling from Brighton to Bradford, had been due to catch a service from King's Cross.
She was directed to St Pancras, but said the platform was "chaos". She later managed to get on a Virgin train at Euston.
"I had to pay for an upgrade to first class because there were no seats or anywhere to stand in standard class," she said.
"People are standing in the aisles or sitting on suitcases - there are elderly people and children with nowhere to sit.
"There were so many people at King's Cross and there was no information coming back to people, and the staff were really overwhelmed.
"St Pancras was chaos with hundreds of people trying to get up to Sheffield on the East Midlands line. You couldn't get on the platform - you could hardly get off the escalator."
A spokeswoman for East Coast said: "Approximately 200 metres of overhead equipment is damaged, affecting all four lines.
"As a result, no services are currently able to operate between Grantham and Peterborough.
"Shuttle services are running between London King's Cross and Peterborough, and between Grantham and destinations north.
"Network Rail engineers are on site and are working to fix the problem as quickly as possible.
"Due to the extent of the damage, passengers are being advised not to travel, to expect major disruption on the East Coast Main Line for the rest of the day and to seek other routes for their journeys wherever possible."
Tickets for travel on Saturday will be valid on Sunday, she added.
The company said it was not yet clear how the power lines, between Grantham and Stamford, had been damaged.
They said tickets would be accepted on East Midlands Trains, Grand Central and First Hull Trains and they said Virgin Trains, First TransPennine Express, Northern Rail and CrossCountry were accepting passengers on any "reasonable alternative routes".
People wanting to know how their journeys would be affected are advised to call TrainTracker on 0871 2004950.