SUFFOLK, Va. (AP) — A wildfire raging in the Great Dismal Swamp National Wildlife Refuge grew to 5,700 acres Thursday as it spread from southeastern Virginia into North Carolina, spewing enormous plumes of smoke visible in satellite photographs taken from space.

Barb Stewart, a National Parks Service information officer, said the blaze is the swamp’s largest in recent history, surpassing a 2008 fire that burned nearly 4,900 acres. It is expected to continue to grow, battled by nearly 160 firefighters from around the country whose ranks are also still growing.

Firefighters doused flames with water and worked to create a “fuel break” around the perimeter by clearing fallen tree limbs and other materials that would further feed the fire.

Stewart said the planned containment area is 20,180 acres, or about 17 percent of the combined acreage of the refuge and the Great Dismal Swamp State Park in North Carolina. The firefighters are backed by four helicopters being used to dump loads of water taken from Lake Drummond within the refuge.

No homes or other buildings are threatened by the fire, Stewart said, but the thick plumes of smoke have created unhealthy air, especially for those with respiratory problems.

Tom Mather, spokesman for the North Carolina Division of Air Quality, said the smoke “is affecting a pretty broad area of the northeastern part of the state,” with localities closest to the fire being given “code red” designations for unhealthy air.

“We’ve been telling people if they see haze and smell smoke, air quality is not good and they should limit outdoor activity,” Mather said.

North Carolina was most affected by the smoke Thursday because the wind was blowing from the north.

Dan Salkovitz, a meteorologist for the Virginia Department of Environmental Quality, said communities along the state border will be affected Friday when the wind shifts from the east. The forecast for Saturday calls for wind from the south and east, he said, which means the smoke is likely to be pushed toward central Virginia.

Refuge officials say lightning started the fire, which was reported Aug. 4. The fire has spread relentlessly because of dry conditions, wind and an abundance of fuel left on the ground from Hurricane Isabel in 2003 and from the 2008 fire.

“The big stuff that got killed by the previous fire has fallen over and spent three years drying out,” Stewart said.

She said the high temperature reached 98 degrees Wednesday.

“There’s been persistent drought in the area, so the fire is not just burning on the surface but down into the organic soil,” Stewart added.

Salkovitz said smoke from that type of fire is especially problematic.

“It’s an acrid smoke, very irritating” to the eyes and throat, he said.

Stewart said the fire could continue to smolder for weeks.

“We need at least six inches of rain over a few days without much wind,” she said.