SANTA FE, N.M. (AP) — Campgrounds and a horse ranch were evacuated Monday as wildfire swept through a Civil War-era historical site in southern New Mexico.

Ground crews, air tankers and helicopters joined efforts to contain a blaze that damaged several buildings at the Fort Stanton Historical Site, authorities said. The wildfire scorched more than a half square mile of terrain at the site and surrounding conservation lands managed by the federal Bureau of Land Management.

Three Fort Stanton structures were damaged, said Laura Rabon, a spokesperson for a multi-agency team responding to the situation. It was unclear which buildings were hit by fire. An advisory from the historical site said the fire entered a former World War II internment camp.

Rabon said the fire was uncontained as crews cleared lines of vegetation on the north side of the wildfire and helicopters doused smoldering hot spots with water.

The blaze at Fort Stanton is about 15 miles away from communities at Ruidoso that were ravaged by wildfires last year when several hundred homes and businesses were destroyed. Those fires were followed by devastating flooding and erosion in scorched areas.

Fire activity at Fort Stanton decreased amid mild high temperatures Monday of 75 degrees and 10 mph winds. The source of the fire was unknown, with a BLM investigator scheduled to begin work Tuesday.

Horses and a family of four were evacuated Sunday from a private ranch in the vicinity, but they had been allowed to return.

On Sunday, air tankers dropped fire retardant on the outskirts of the fire in efforts to slow its progress.

Highway 220 was closed near Fort Stanton to ensure access for firefighting crews. Three camping areas were evacuated and closed.