The incident was at the Kettering North Junction and is currently affecting East Midlands Trains services on the London St Pancras/Nottingham/Sheffield and London St Pancras to Corby routes.
Although the line has reopened, all trains on the route will be delayed in either direction between Kettering and Leicester.
It is expected that normal service will resume at about midday.
Until then, the following advice has been issued by East Midlands Trains:
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Customers travelling to/from London from Leicester & the North should use alternative routes.
Advance purchase ticket may be used on other trains, than booked on the affected route.
Off peak tickets may be used on other trains, than booked on the affected route.
Our trains are likely to experience extended delays or alterations. Trains are also extremely busy. You should use alternative routes which remain the most comfortable and quickest journey options.
Other train operators will accept East Midlands Trains tickets.
Sheffield to London Kings Cross via Doncaster.
Derby to London Euston via Birmingham.
Nottingham to London Kings Cross via Grantham.
Leicester to London Euston via Birmingham.
Replacement buses are for the customers travelling locally to Market Harborough, Kettering & Wellingborough.
A replacement bus service is running in both directions between Leicester and Kettering only every 60 minutes, departing on the hour from Leicester and returning on the hour from Kettering.
A replacement bus service is running in both directions between Leicester and Kettering, stopping at Market Harborough every 60 minutes, departing at half past the hour from Leicester and returning at half past the hour from Kettering.
An hourly shuttle bus will be operating between Kettering and Corby and will depart Kettering on the hour and Corby at twenty past the hour.
These arrangement will remain in place until the train service recovers.