Twelve people were injured after a man sprayed acid inside a nightclub in East London’s Hackney early on Monday, BBC reported. Ten of the injured sustained minor injuries while two men, in their twenties, were reported to be in serious condition.

The incident took place in Mangle E8 on Sidworth Street, Dalston, and is believed to have occurred after a dispute between two groups of people. “The only information that we have is that an unknown corrosive substance was thrown inside the nightclub,” a London Fire Brigade spokesperson told BBC.

Phie McKenzie, who was across the road at Martello Hall, tweeted a photograph showing stretchers and firefighters outside the club, local newspaper Hackney Gazette said. “Scary scenes in Hackney tonight,” she tweeted. “We have heard reports of chemical burns of people in the building here.”