CUMBERLAND ISLAND - Authorities investigating a 43-acre wilderness fire on Cumberland Island believe it was started by a person, but don't suspect it's a case of arson, the National Park Service's top official on the island said Wednesday.

Superintendent Fred Boyles declined to give further details on the cause of the fire, which has been burning since Jan. 4 in dense woods on Georgia's largest barrier island, other than to say it was "human-caused." He said the investigation still isn't complete.

"Do we believe that it was an arson-caused fire? The answer is no, we do not," Boyles said. "It was certainly not intentionally started by anyone."

Even if arson isn't suspected, whoever is responsible could face criminal charges. Starting campfires or any other fire is strictly prohibited in Cumberland Island's federally protected wilderness area.

Firefighters, using hand tools, surrounded the blaze with containment lines last week in an effort to hold its footprint to less than a tenth of a square mile. Officials hope the fire will eventually burn itself out and soaking rains Wednesday helped knock down some of the remaining flame and smoldering hot spots, Boyles said.

Meanwhile, rangers said Wednesday they're reopening one of the two campgrounds they were forced to closed last week because of the blaze. The other campground remains off-limits to visitors.

Otherwise Cumberland Island has remained open to tourists, with the fire affecting just a fraction of its total 40,000 acres. The fire has posed no threat to the island's historic structures such as the 19th century mansions built by wealthy industrialists long before the federal government bought the island in 1972.