Dozens of Tube commuters have been evacuated through a tunnel amid reports of smoke on a train.
Fifty-nine passengers were escorted off the service after it stopped between Bond Street and Baker Street stations.
Four people were treated at the scene for smoke inhalation, but were not taken to hospital. Transport for London (TfL) has been approached for comment.
Firefighters said a mechanical failure may have caused the smoke, while police said there was no fire onboard.
The Jubilee Line was shut between Finchley Road and Waterloo throughout the rush hour.
Four crews of firefighters - from Soho, Paddington and North Kensington fire stations - were called at 05:54 BST and left at 07:18.
TfL initially said the Jubilee Line disruption was being caused by a "track fault at Bond Street".
A spokesman for London Ambulance Service said "a number of resources" were sent to Bond Street station including a specialist hazardous area response team.
He added: "no patients were taken to hospital".