Dozens of party-goers were injured after a second-storey back deck abruptly collapsed during a wedding bash in Langley, B.C.

Emergency crews were called to a home on 268th Street shortly after 5:30 p.m. on Friday evening.

Witnesses told CTV Vancouver the back deck was filled with guests when it suddenly crashed down.

“I heard this boom,” next-door neighbour Charles Edward Ford recalled. “I thought something exploded.”

“It just collapsed on one side and all the people, they just like [went] into a slide. They just went down,” wedding guest Moninder Gill.

Officials said the deck became detached from the home and collapsed.

Police, firefighters, and the B.C. Ambulance Service responded to the scene where they found up to 40 people injured.

“There was screaming, crying, a lot of the injuries were ankle, back, knee-related,” Ford said. “People were unconscious.”

Officials said one person was airlifted to hospital in critical condition while two others were transported by ambulances. RCMP Cpl. Craig Van Herk told The Canadian Press that nearly 20 people suffered serious injuries, while 12 to 15 others were treated in hospital for minor injuries.

Amarjit Gill was on the deck when it fell, but she was unhurt. She told CTV Vancouver that she saw a 14-year-old boy with a broken leg.

It’s still unclear exactly how many guests were on the deck when it collapsed, but Van Herk said there were more than 100 people at the party.

With files from The Canadian Press