UPDATE: Holborn station has now reopened and services on the Central Line have resumed, but TfL is still warning of severe delays
Holborn station has been closed due to a fire alert amid reports of smoke.
Police officers and the London Fire Brigade are attending the incident.
Eye-witnesses have reported hearing a loud bang and smoke coming from a Central Line train.
Transport for London has told travellers to take alternative routes and the Central Line has been part suspended between Liverpool Street and White CIty on the westbound line. Severe delays are affecting the rest of the line as a result.
London Fire Brigade said two fire engines and 10 firefighters are at the scene.
Last week Oxford Circus station had to be evacuated after an electrical fault on a Bakerloo Line train. Four people were treated for smoke inhalation.
Elsewhere in London, there is major disruption at Waterloo on Tuesday morning after a train derailment and a train hit buffers at King's Cross station.
This breaking news story is being updated as more information emerges - please refresh the page for the most recent version.