Oxford Circus station has been evacuated following reports of smoke issuing from an escalator machine room.
Firefighters were investigating the reports on the northbound Victoria line this morning.
London Fire Brigade said it was called at 8.34am when smoke was spotted near the northbound Victoria Line platform.
The force said Oxford Circus station was “evacuated as a precaution”.
TFL Access tweeted: “This station is closed while we respond to a fire alert.”
Tickets are being accepted on London buses.
Video footage shows the police and firefighters surrounding the station’s entrance, which has been taped off.
It comes as TFL urged the public not to travel during the extreme heat which is predicted to peak today, with parts of the UK expected to reach 40C.
Amber and red extreme heat warnings have been implemented across the nation for the duration of the heatwave.
There are currently severe delays on the Central, Bakerloo and District lines due to heat-related speed restrictions.
The Hammersmith and City line is suspended, while London Overground and Metropolitan lines are part-suspended due to the weather.
Network Rail revealed that the hottest railway track reached a blistering 62C on Monday.
It tweeted: “Our hottest rail recorded yesterday was 62C, in Suffolk! Rail temperature can be about 20C higher than air temperature, causing it to expand, bend and break.”
Transport secretary, Grant Shapps, told people to “apply common sense” when travelling in the heatwave and “depending on the nature of your journey and reason for it, you might want to consider rearranging your day around it”.
It comes after millions of Britons experienced sweltering temperatures on Monday night, with the Met Office confirming that provisional data indicates it was the warmest night on record.
Health authorities have urged people to stay inside during the hottest period of the day, between 11am and 4pm, and wear sun cream, a hat, stay in the shade and keep hydrated with water.
TfL have confirmed that Oxford Circus has now reopened to travellers following a two and a half hour closure.
