Firefighters are battling a blaze on more than 100 acres of forest in Atlantic County, authorities said this afternoon.

The fire, on private land and in the Great Egg Harbor River Wildlife Management Area in Hamilton Township and Folsom Borough, is 25 percent contained, according to Acting State Forest Fire Warden Michael Drake. It is expected to be fully contained later this afternoon.

No homes or property are threatened by the blaze, which is about a half-mile northeast of Route 322 and Eighth Street in Folsom Borough, Drake said.

The blaze spread from an illegal debris fire set Wednesday night, Drake said. At 7 a.m., when it was reported by a private crop-dusting company, about 30 acres were involved.

The fire is expected to be held to about 125 acres, Drake said. Ten engines, a helicopter, and 30 members of the state forest fire service are at the scene, he said.