Some 2,000 people have been evacuated from a street in Holborn in central London. Six fire engines and 70 firefighters were called to the scene on Kingsway after an electrical fire broke out under the pavement.
According to a statement from London Fire Brigade, the alarm was raised around 12:40p.m. local time (13:40 UTC) on Wednesday after smoke was seen coming our of an inspection cover on the pedestrian path.
London police later declared the fire a "major incident."
Thousands of Londoners were evacuated from nearby buildings, including the Civil Aviation Authority's headquarters and part of the London School of Economics, as the capital's fire brigade implemented a 25-meter safety cordon.
Footage posted on social media showed flames breaking through a manhole plumes of thick black smoke filling the streets as fire services waited for utility companies to disconnect the power supply before they were able to tackle the blaze.
"We can see flames coming out of the pavement which looks quite dramatic, but that is the gas pipe - it has now ruptured and that has now ignited and the gas is burning off and, if anything, makes it safer for us as the gas is being burnt off," Gary Squires, from London Fire Brigade told radio station BBC London 94.9
The Holborn tube station was closed and several neighboring buildings also suffered power cuts.
A number of theater productions were also cancelled as a result of the incident, including "Letters Live" at Freemasons' Hall, which curently stars Oscar-nominated actor Benedict Cumberbatch.
No injuries were reported.