Forest rangers and local fire departments battled a large forest fire Friday afternoon on Sheep Island in Casco Bay.

Forest rangers said the fire threatened four structures while it was active, but it was contained shortly before 6 p.m., WCSH-TV reported.

Plumes of white smoke rose from the fire, and a ranger helicopter was sent to the island, according to a tweet from the Maine Forest Service.

As the fire was underway, photos and statements posted on Twitter from the forest rangers indicated that several homes were in danger and that the chopper was to begin dropping buckets of water onto the flames.

Sheep Island is located off Harpswell.