Firefighters were called to reports of smoke on a tube train between Bond Street and Baker Street stations this morning.
The smoke is believed to have been caused by a mechanical failure.
Crews evacuated 59 people from the tube train via the tunnel. Four people were treated at the scene for shortness of breath by London Ambulance Service crews.
The Brigade was called at 0554 and the incident was over for firefighters at 0718. Four fire engines and around 25 firefighters from Soho, Paddington and North Kensington fire stations attended the scene.