Commuters are facing delays and disruptions on the railway after fire damage to a signalling system in the West Midlands.
Services were cut in half on Thursday morning
Services between Birmingham and Coventry are severely disrupted by the problem at Birmingham International.
A spokeswoman for Network Rail said a signal had been damaged by fire at Marston Green. Repair work could last until the evening or Friday morning.
Virgin and Central Trains are being affected by the work.
The spokeswoman said: "Unfortunately this will have a severe knock on effect for customers travelling between Birmingham and Coventry and travelling to London Euston."
The fire is thought to have been started in an arson attack but this has not been confirmed by British Transport Police.
A spokesman for Central Trains said the fire started shortly after 0500 BST meaning commuters had a difficult journey.
"Services were cut in half, some were diverted and others turned back.
"By the end of the day we should have a system up and running so people can get home safely," he said.
A Virgin Trains spokesman said it was a difficult situation and trains would be disrupted until repairs could be made.
"We are providing coach transport where necessary and some trains will be diverted.
"We are running the best service we can but there will be some disruption," he said.
Commuters also faced problems between Leicester and Birmingham due to a broken down freight train on Thursday morning.