A person has died on the tracks at Gloucester Road station, causing delays on the Piccadilly Line.
Westbound services between Hyde Park Corner and Acton Town were stopped while police and paramedics dealt with the incident.
The line is now running with severe delays.
Emergency services were first called to the scene at 3.16pm.
Transport for London said that the London Ambulance Service and British Transport Police were also in attendence.
A BTP spokesman said: “We were called to Gloucester Road Tube station at 3:16pm on Tuesday 25 February following a report of a casualty on the tracks.
"Officers from BTP attended alongside paramedics, but sadly a person was pronounced dead at the scene.
"The incident has been declared non-suspicious.”
The Circle Line, which also runs through the station, is also running with severe delays.
There are also minor delays on the Victoria Line and District Line.
On the Metropolitan Line, there is no service between Moor Park and Watford due to a signal failure at Croxley.
