Passengers travelling by train from Corby, Kettering and Wellingborough are facing delays and cancellations this morning (Tuesday).
There is damage to the overhead electric wires at Luton between Luton and Luton Airport Parkway, disrupting East Midlands Trains on the Sheffield/Nottingham/London routes.
Network Rail have engineers on site investigating the problem.
Trains between London St Pancras and Corby are suspended.
Other trains will be delayed by 15 to 20 minutes in the London direction between Luton and London St Pancras.
An East Midlands Trains spokesman said: “You should continue to travel as originally planned however your journey may be delayed by up to 30 minutes. We are sorry for the delay to your journey today.
“Our trains are likely to experience extended delays or alterations.”
A rail replacement bus service will be in place between Corby and Kettering from 10.45am.
These arrangements will remain in place until the line re-opens and the train service recovers.
An East Midlands Trains spokesman said: “We have no estimate of when the lines will fully reopen or when our normal service will resume.”