A derailed train between Penrith and Oxenholme means all lines are blocked
Other emergency services personnel are also at the scene and are "currently assessing the situation".
National Rail said the incident happened between Penrith and Oxenholme, affecting trains running between Carlisle and Preston.
One passenger on board told LBC the train had "hit a landslide" causing the incident.
Initial reports suggest the train remains upright with no injuries currently reported.
The passenger told LBC that 46 people currently remain aboard the train.
us are still on the train, we hit a landslide. Crew and emergency services have been amazing. We are being taken to Shap Wells Hotel.
An Avanti West Coast spokesperson said: “At 06.10hrs today, 3 November, the 0428 Avanti West Coast service from Glasgow to Euston was reported to have derailed at Shap in Cumbria.“Our priority is the wellbeing of everyone who was board and getting them safely off the train.
"We are assisting emergency services who are on the scene.“As a result, all lines are blocked north of Preston.
"Please do not attempt to travel north of Preston today.“We’ll provide further information in due course, but it is likely there will be significant disruption to our network for a number of days.”
It comes as Transport Secretary Heidi Alexander told LBC a major incident had been declared, explaining: "I have been informed of this incident within the last half an hour or so.
"I know that a major incident has been stood up. There are no reported injuries.
"We will work swiftly to make sure that people can get off the train safely.
"I will be remaining in constant touch with the train operating company and the railway accident investigation branch."
"We will work swiftly to make sure that people can get off the rain safely. I will be remaining in constant touch with the train operating company"
National Rail said: "Major disruption between Carlisle and Preston expected until the end of the day.
"A derailed train between Penrith and Oxenholme means all lines are blocked. Trains running between Carlisle and Preston may be delayed by up to 120 minutes or cancelled."
It comes as a North West Ambulance Service spokesperson said: "Following reports of a train derailment near Shap in Cumbria, the trust has dispatched resources to the scene.
"We are currently assessing the situation and working with other members of the emergency services.
"Our priority is to ensure people receive the medical help they need as quickly as possible."
The operator that major disruption is expected until the end of the day.
