Greater Anglia passengers are being advised not to travel due to overhead wire problems near Colchester.
The overhead wires between Colchester and Marks Tey became damaged some time in the early hours of this morning.
As a result, 12 trains between East Anglia and London Liverpool Street have been cancelled, while many more have been delayed or will be terminated at Ipswich.
Disruption is expected until at least 2pm.
Greater Anglia tickets are being accepted on Great Northern services between Cambridge and London Kings Cross, while customers at Norwich can travel to London Liverpool Street via Cambridge on Greater Anglia Services.
In a statement, Greater Anglia announced: "Due to the overhead wires being damaged between Colchester and Marks all lines are blocked. Customers are advised NOT to travel between in/out of Liverpool Street via Colchester until further notice."
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