The Piccadilly Line is still part suspended following the derailment of a London Underground train in the early hours.
The train, which had no passengers on, came off the rails between Gloucester Road and Earl's Court at 0500 BST.
Transport for London (TfL) said nobody was hurt in the incident, which involved an engineering train.
The Piccadilly Line is currently suspended in both directions between Hammersmith and Green Park.
A TfL spokeswoman said: "The incident occurred during engineering hours before the start of passenger services and there were no injuries."
She continued: "London Underground is currently investigating and is working to restore services on the Piccadilly line as quickly as possible. A good service is operating on all other London Underground lines."
It is not yet clear if the engineering train was operated by London Underground or the maintenance contractor Tube Lines.
Tube tickets are currently being accepted on local buses and on the Heathrow Connect.
About 600,000 commuters use the Piccadilly Line every day.