The incident was reported between Grantham and Peterborough just before 12.45pm today (November 5).
All lines through Grantham are closed as the incident is being dealt with.
LNER services between Inverness and London Kings Cross and LUMO trains between Edinburgh and Kings Cross are unable to run until further notice.
Trains may be cancelled, delayed by up to 60 minutes or revised.
Major disruption is expected until 4pm.
We have contacted British Transport Police for further information.
If you’ve been affected by what happened on the network today, there is always someone to talk to.
You can contact the Samaritans on 116 123 from any phone for a confidential chat.
