Passengers were evacuated after a fire broke out on a train between Sheffield and Derby.
Trains between London St Pancras and Sheffield after affected.
An East Midlands Train spokesman said trains are also unable to run on the Nottingham-Derby-Matlock route.
He said: "There is a fire on a train between Derby and Chesterfield which is currently being evacuated.
"This is disrupting our trains on the London St Pancras-Sheffield and Nottingham-Derby-Matlock route.
"At present Network Rail are aware and emergency services are on their way.
"All our trains on these routes cannot run in both directions between Derby and Chesterfield/Matlock.
"Our trains to and from London St Pancras will be diverting where possible and will add up to 30 minutes to your journey.
"We are expecting the line to fully reopen in the next two hours whereby our normal train service is expected to resume on the affected routes at around 3pm.
"If you are travelling between these stations your journey may be delayed by 60 minutes.
"Customers travelling between Derby and Matlock are advised to use the rail replacement buses which have now been sourced.
"Customers travelling to and from Sheffield may use alternative trains to/from London St Pancras via Doncaster. Also customers may also use their tickets on Cross Country services between Derby and Sheffield once the service resumes."