There are delays of up to half an hour on trains between Peterborough and London today, Thursday December 17.
Speed restrictions have been imposed near Huntingdon and there is also a signalling problem at London Kings Cross.
Disruption is affecting Grand Central; Great Northern; Hull Trains and Virgin Trains East Coast. This is expected to continue until 15:00.
You can follow the incident using the hashtag #KingsCross on Twitter.