Firefighters in London say a pigeon that was holding a lit cigarette in its mouth is responsible for the blaze that nearly burned an entire apartment building down last night. 

According to BBC News, investigators with the London Fire Brigade believe the bird took the cigarette butt to its nest atop the building, resulting in the Wednesday night fire. "The smoking gun was found when we discovered a partially burnt birds nest," Matt Cullen explained to the BBC. 

The BBC adds that the fire damaged roughly a fifth of the building, while nine residents were evacuated. 

[via BBC News]