Scores of people fled a fire that broke out at a nightclub shortly after sparklers were lit on the dance floor.
It is thought more than 100 people escaped the blaze in Clapham, southwest London in the early hours on Sunday.
Footage shows clubbers screaming and running from the flames at the Little Orange Door bar.
Earlier, revellers had been waving sparklers as Katy Perry’s “Firework” blared over the speakers.
One person was taken to hospital and four others were treated for smoke inhalation at the scene, the London Fire Brigade said.
Clubbers suffered burns, cuts and bruises as they scrambled to safety.
Erin Doyle was out with 30 friends celebrating her 26th birthday – but ended up running for her life.
“I thought if anyone dies it’s my fault they’re here,” she said.
She described seeing the bar’s orange curtains going up in flames.
“There was smoke everywhere and fire started coming across the ceiling. Everyone was in shock. I started running and people stampeded to try and get out.”
There was a bottleneck as people streamed towards the doors, and some of her friends cut themselves crawling over furniture in front of a fire exit, she said.
Four fire engines and around 25 firefighters were called to the blaze near Clapham Common. Around 60 people left the building before crews arrived.
A spokesperson for the London Fire Brigade said it is believed the fire was accidental and “involved an indoor firework.”
Firefighters were called shortly after midnight and had the blaze under control in just over an hour.
Part of the ground floor was damaged and the bar has since closed.
The Little Orange Door said it was “devastated”.
“We are incredibly relieved that no one was seriously injured and that it was contained quickly,” it said in a statement on social media.
“To all those in attendance: we are truly sorry. We are taking this incredibly seriously and understand how scary it must have been.”
The bar said it was carrying out an investigation, adding: “We will take every step necessary to make sure this never happens again.”