Pssengers using East Midlands Trains' services between Nottingham and Worksop are currently facing disruption because of a fault with the signalling system at Kirkby.
A spokesperson for East Midlands Trains said: "We are currently unable to run our trains between Nottingham/Mansfield/Worksop in either direction.
"At present we are expecting the line to reopen in the next two to four hours.
"It may then take a further hour to reintroduce our timetable on the affected route.
"At present Network Rail have specialists on site working to fix the fault."
The spokesperson added: "We are running rail replacement buses between Nottingham/Mansfield/Worksop in place of the services that we are unable to run.
"This will mean that journey times are extended.
"Please allow extra time to travel."