Rail passengers have been warned of major disruption caused by lightning striking a signally system in Norfolk.
Greater Anglia said all lines were blocked after the damage at Harling Road, at East Harling.
Train services between Norwich and Cambridge and Norwich and Stansted Airport had been suspended, with disruption expected until 18:00 BST.
Greater Anglia said it had been unable to find replacement buses due to engineering work taking place elsewhere.
It has advised passengers not to travel between Norwich and Cambridge via Thetford and Ely.
Network Rail had assessed the damage and said it had affected the signalling system in the area including multiple level crossings and multiple axle counters, which help monitor speed, direction of travel and the time it takes for a train to travel.
“Response teams have been deployed to investigate and rectify the issues, but we currently do not have an estimated time of completion for this because of the scope of the work to be carried out,” Greater Anglia added.
“There will be no trains or replacement buses between Norwich and Cambridge via Thetford and Ely until further notice.
“We have been unsuccessful in sourcing replacement buses because of engineering work taking place in other parts of the network this weekend and limiting resources.
“Please do not attempt to travel on this route.”
It said tickets dated for Sunday would be accepted for travel on Monday.
It has advised customers to use services that stop at Stowmarket for onward journeys to Norwich or Cambridge.