A driver suffered minor injuries when his London Overground train hit the buffers at a London rail terminal station.
The driver was taken to hospital and was later discharged.
An investigation has been launched into the collision.
Rory O’Neill, Transport for London’s General Manager for London Overground, said: “An out-of-service London Overground train was involved in a low-speed collision with a buffer stop at Liverpool Street station at around 0100 this morning.
“The driver sustained minor injuries and was taken to hospital as a precaution.
“They have since been released.
“A full investigation is now taking place to establish the circumstances surrounding the incident.”
The incident happened at Liverpool Street Station
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Greater Anglia said early on Thursday “Due to an operational incident between London Liverpool Street and Hackney Downs some lines are blocked.
“Train services running to and from these stations will be cancelled or diverted.
“Disruption is expected until the end of the day. Platforms 1, 2 and 3 at London Liverpool Street are currently closed.”
Routes affected by the disruption included services from London Liverpool Street to Stansted Airport, Cambridge North and Hertford East.
Services between Liverpool Street Station and Hackney Downs and Chingford were also impacted.
Greater Anglia added: “As there are fewer platforms available at London Liverpool Street, some trains will terminate at Bishops Stortford or be diverted to Stratford.
“Trains arriving into / departing from London Liverpool Street may incur a small delay. If your train is cancelled, terminated early or diverted to Stratford you can use your ticket to travel on the train before or after your booked service.”
Some services, including to Cambridge North and Chingford, were being cancelled mid-afternoon, with others delayed.