Around 2,000 people have been evacuated and a tube station closed after an underground fire in central London this afternoon.
Police have declared a major incident over a blaze which began under the pavement of a main road on Kingsway in Holborn, the fire brigade said.
Office workers and pedestrians were evacuated while firefighters tackle the electrical blaze, which started among cables.
The alarm was raised after a large amount of thick black smoke was seen coming out of an inspection cover on the pavement.
Six fire engines and 35 firefighters and officers are at the scene, where a large safety cordon is in place.
Among those evacuated in the area were judges, lawyers and staff at the nearby Royal Courts of Justice on the Strand.
Onlookers reported "struggling to breathe" and "chaos" in the area as those evacuated waited on the street and traffic began to pile up.
Nicola Foxfield, 29, said: "I was walking from Covent Garden towards Holborn and I could smell burning in the air.
"As I got closer I could see fire engines everywhere then I could see loads of thick, brown smoke rising off the road.
"It's chaos and fire engines are coming from every direction and there are so many people around."
Another witness said he "struggled to breathe" as smoke seeped through the drains as he walked along Aldwych, at the bottom of Kingsway.
He said: "I had just cycled over Waterloo Bridge and as I approached Kingsway I saw a big crowd of people and smoke billowing towards me.
"The fire crews and police officers were beginning to cordon off the area. I was close enough to see thick black smoke puffing out of the drain grills and I struggled to breathe.
"Hundreds of people were leaving their buildings on Fleet Street and Kingsway."
Office workers were left waiting on the streets, while nearby shops and cafes were plunged in to darkness.
An LFB statement said: 'Police have declared a major incident and closed Kingsway at both ends. Motorists are being advised to avoid the area.'