LONDON (Reuters) - London's Holborn underground station closed briefly on Tuesday after overheating equipment on a train filled a platform with smoke.
The fire service said it had sent two fire engines and 10 firefighters to the station.
"It was an overheated compressor on a train not a fire," London Fire Brigade said a statement.
A witness on a train at the station said smoke filled one of the carriages.
"There was a fire alert on a westbound Central line train," a spokesman for London's transport operator said. "We are investigating the cause."
The fire service said it dealt with the incident in under 50 minutes.
(Reporting by Andy Bruce, Sarah Mills, Kate Holton, Paul Sandle, Michael Holden and Costas Pitas; editing by Guy Faulconbridge)