As many as 10 people were injured in an explosion at a Jewish festival in Stamford Hill, north London, according to police.
Dramatic video footage was captured by a member of Hatzola, a volunteer emergency medical service, showing the moment of the explosion at the Lag BaOmer celebration.
The fire erupted after a rabbi attempted to light the Medurah (bonfire), according to The Yeshiva World.
Video from Stamford Hill shows an explosion going off off and a large fireball shooting into the air as the pole used to ignite the fire was lit.
Gathered crowds were stood around the explosion when it went off.
The Yeshiva World cited Hatzola as saying its volunteers rushed to the scene and treated around 30 people.
Many of the 10 taken to hospital had burns on their faces, the Orthodox Jewish news website said.
The Board of Deputies of British Jews tweeted thanking Hatzola and the London Ambulance service for their responses.
The cause of the explosion has not yet been confirmed.
Hackney Police this morning said ten people suffered minor injuries following a "large fire" at a Jewish community celebration.
No criminal allegations were reported.
London Fire Brigade said it had responded to several bonfires throughout the Wednesday night.
It urged individuals celebrating Lag BaOmer on Thursday night "to take extra care".