A fault on the network has seen services in and out of London's King's Cross station grind to a halt this morning.
No trains were able to run to and from the station because of damaged overhead wires, operator Great Northern said on Monday morning.
Platforms one to six are now in use, as of 7.30am, but services could still be affected.
The problem with the electricity wires is causing disruption between King's Cross and Finsbury Park, with delays and cancellations expected.
Services to and from King's Lynn, Ely and Cambridge are among those affected.
Trains are able to run to those destinations, though passengers are advised to leave extra time for their journeys.
Disruption is expected until at least 9.30am.
Great Northern said: "Specialist engineers are on site and are investigating the damage to the overhead electric wires."
It comes on the day engineering works begins on the line between King's Lynn and Ely.
Lines will be closed each night from Monday to Thursday this week, meaning a rail replacement bus service will be required after 11pm each day.
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