Fire investigators believe they have determined that a smoker likely caused a fire inside a Fort Point building this week.
A three-alarm fire broke out at 27 Melcher St. about 11 p.m. Monday in a crossover connection two buildings.
Boston Fire officials said the most likely cause was careless disposal of a cigarette.
“A worker who smoked was working on the outside near the roof of the crossover between buildings, where fire started,” according to the fire department.
Two firefighters were injured while fighting the blaze, which caused $200,000 in damage.