Around 100 firefighters are battling a huge blaze near a railway station.
Large plumes of thick, grey smoke are rising from Elephant and Castle station in south London.
A video of the blaze posted on social media showed an explosion leading to a burst of flames.
London Fire Bridge (LFB) said 100 firefighters are tackling the fire, which was first reported at 1.43pm on Monday.
Three commercial units underneath railway arches are “completely alight” and six cars and a telephone box have also caught fire, according to the brigade.
One man is being treated at the scene by London Ambulance Service crews.
The railway station and nearby buildings have been evacuated.
The fire has blocked rail lines running through the station, causing disruption to Thameslink and Southeastern services.
Northern Line services on the London Underground are not stopping at Elephant and Castle tube station, which is separate to the mainline station.
A Metropolitan Police said: “There are significant road closures in place and the public are advised to avoid the area.
“The incident is not believed to be terror-related.”
Transport Secretary Grant Shapps wrote on Twitter: “I am aware of the fire at Elephant and Castle station – my team is working closely with TfL (Transport for London) and Network Rail.
“Advise the public to avoid the area until further update. Thank you to all the emergency services currently in attendance.”
Sara Scarpa, 25, lives in nearby apartment building Hurlock Heights and said smoke and the noise of the explosion had reached her window.
“We opened the window for a sec as you could hear people shouting, and we smelt something very very strong,” she said.
“The smoke (was) dying down a little… we heard an explosion and now it started again.”
A restaurant worker close to Elephant and Castle station said she was evacuated after the fire broke out.
Alex Leckie, 30, assistant manager at Tupi, said: “The entire building was evacuated, we began to smell smoke and the store owner went to check, we saw smoke billowing out and what I’m told is the mechanics were on fire, the smoke pillar started enveloping the apartment blocks as well and we kept hearing intermittent bangs.
“The police have indicated it could be some time (until they are allowed back inside). They have repeatedly pushed the crowds back even from the Castle Square Park and cordoned off the roads, there is a very, very heavy presence.
“At this point emergency crews have everyone well clear of the area.”
Martin Bobrowski, a builder who is working opposite the station, said he heard ambulances and police driving nearby before seeing smoke coming from the station at about 2pm.
“I heard the police come and I thought there was an accident nearby, but then they started blocking the road off. I then came outside for a cigarette and saw all the black smoke,” he told the PA news agency.
“I was really surprised to see it and a bit scared.
“They haven’t told us anything.
“The smell was awful.
“It smelt like a burning electrical cable smell.”
Officers at the scene said the station has been fully evacuated along with the nearby Strata residential building.
They described it to local residents as a “major incident”, adding that road closures are going to be in place for “several hours”.