Chaos was sparked on the London Underground on Friday evening, as passengers were forced to smash through windows to escape a train as carriages began filling up with smoke.
Shocking footage from Clapham Common showed panic at the tube station as commuters were left trapped inside carriages with doors stuck and refusing to open.
People could be heard crying in terror as others begin smashing the windows to try and get them out in what is understood to be a "fire alert".
In the distressing footage, some commuters tried to wrench the doors open but they were seemingly stuck, as The Mirror was told that the carriages were filling up with smoke inside.
Meanwhile, workmen had to smash through the windows as an overhead sign can be seen telling people to evacuate the station.
When the windows were broken and smashed through, dozens of commuters clambered out, fearing for their safety had they stayed inside.
One of the horrified Brits who was trapped inside the carriage told the Mirror how the carriages began filling with smoke as the doors wouldn't open.
Jake Sharp told the Mirror the only reason people were able to escape was because of workmen on the platform who had their tools with them and were able to smash the windows.
They described the situation as "turning into hysteria" within the carriages as they filled up with smoke as the driver told them nothing and left the panicking masses in the dark as they could see others running from the train on the opposite platform out of the station.
The 32-year-old said: "There was a smell of smoke on the train. The train went down about five carriages into the tunnel and stopped, the train on the opposite side pulled in and people were running to get off the platform.
"The whole time the carriages were filling with smoke and the doors did not or would not open and when we tried to open them they only opened maybe 10cm.
"Thanks to the workman on the platform on their way home they had hammers and other tools to smash all the windows for everyone to get out, no response from station staff at all even with everyone’s scream for help."
They admitted they weren't sure if everyone made it out okay, but described it as "absolute carnage".
Before the workmen were able to smash the windows, some people were able to squeeze through the narrow gap in the doors as others could pull them through.
They added that if the workmen hadn't been present, they would "dread to think what could have happened".
In the shocking aftermath, shell-shocked commuters could be seen walking along the platform beside the destroyed tube train, stepping on glass.
Outside the station, people were being diverted away and fire engines were present.
A TfL spokesperson said: “We’re sorry for the distress caused at Clapham Common. The London Fire Brigade attended the station and confirmed there was no fire. We are investigating the details of this incident."
Another commuter caught in the chaos was Nigel Ingofink, who was at the front of the train, left in the dark for "several minutes" when it first abruptly stopped.
He told the Mirror: "The train stopped suddenly with half the carriages in the station (I was in the tunnel at the front of the train).
"No movement or announcements for several minutes. Then lights went out and we could hear screaming towards the rear.
"Finally the driver told us to walk to the rear of the train and we exited a set of open doors to witness the scene of broken windows on the platform where other passengers had obviously panicked.
"There was a strong smell of burning around the carriages with the broken windows."
British Transport Police later confirmed the incident was likely caused by a faulty train.
It tweeted: "We received a report of a faulty train at #ClaphamCommon shortly before 6pm this evening, and we are aware of a video showing passengers trying to leave the train.
"The issue is believed to have been caused by brake dust which can often be confused with burning."
The London Fire Brigade confirmed this, saying there was no evidence of a fire.
A spokesperson said: "Firefighters were called to a report of smoke issuing from a train at Clapham Common Underground Station this evening (May 5).
"Crews attended but following investigation, found no sign or evidence of a fire. Investigations are ongoing but the report of smoke is believed to have been caused by the train's brakes.
"Around 500 people left the train before firefighters arrived. The Brigade has not received any reports of injuries.
"The Brigade was called at 1752 and the incident was over for firefighters by 1829. Crews from Battersea, Tooting and Brixton fire stations attended the scene."
