Investigators are looking at a possible electrical fault as the potential cause of a fire that heavily damaged a structure at a Melville day camp Thursday.

The fire at the Crestwood Day Camp was reported in a 911 call at 6:21 p.m., Suffolk County police said.

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Volunteers from the Melville, Huntington Manor, Dix Hills, Plainview, East Farmingdale and Farmingdale fire departments responded to battle the blaze, which police said collapsed the roof of one of the structures.

The camp was unoccupied at the time, police said.

Police said Arson Squad investigators and the Town of Huntington fire marshal also responded to the scene and the cause of the fire remained undetermined on Friday, but said investigators were looking at a possible electric fault as the cause.