Holborn fire: Chaos as 2,000 people evacuated to escape toxic smoke in central London

Firefighters said an electrical fire had started under the pavement

Flames are seen escaping from a manhole cover as fire crews tend to the underground cable fire at Lincoln's Inn Fields (Getty)

More than 2,000 people were evacuated from buildings in central London this afternoon as toxic smoke filled the streets.

The Metropolitan Police declared a "major incident" after blocks housing businesses and part of the London School of Economics were cleared by the emergency services.

As the smoke spread, Holborn Tube station was closed and the Royal Courts of Justice also had to be evacuated along with some nearby West End theatres, meaning shows were at risk of being cancelled.

Underground fire in Holborn, central London. pic.twitter.com/6Az4djVXF9

— Rickin Majithia (@rick_maj) April 1, 2015

After battling the fire for around nine hours, the London Fire Brigade has tweeted to say that the blaze is under control, but around 21 firefighters will remain at the scene overnight to monitor the situation.

Benedict Cumberbatch's appearance at Letters Live at the Freemasons' Hall was among the events called off.

Firefighters said the fire started among power cables beneath the pavement in Holborn and they could not put it out until the current was switched off.

The blaze was believed to have originated in a service duct that carries gas, electric and water through the capital.

The London Fire Brigade worked with utility companies to find the source of the fire, which appeared to be worsening hours after it began.

Footage from a Sky News helicopter captured flames bursting out of one manhole in a closed off road after a gas main ruptured underground.

Photos from the scene showed the air filled with dark smoke that appeared to be streaming from potholes and underground vents.

People were seen pouring out of offices, restaurants, cafes and shops while roads were cordoned off by the emergency services.

Onlookers described "crazy scenes" and "madness" as smoke rose so high in the air that it could be seen from the Shard skyscraper.