Trains to and from London are being disrupted due to a major signalling problem between Bedford and Luton.
Currently, no East Midlands Trains services are running between Bedford and London St Pancras.
Southbound trains are instead terminating at Kettering, with northbound services stuck at Luton.
Passengers are being advised to travel via another route wherever possible.
Network Rail engineers are on site working hard to repair the fault, however there is currently no confirmed estimate of when services will return to normal.
A spokesman for East Midlands Trains said: “Services on our network are being severely disrupted by a signalling problem in the Leagrave area.
“We would like to apologise to passengers for any inconvenience this disruption may cause and would like to thank them for their patience as Network Rail works hard to restore services to normal as quickly as possible.”
Passengers can view more information at www.eastmidlandstrains.co.uk or by calling TrainTracker on 0871 200 49 50.