A smoky mulch fire at Ladson Wood Recycling Thursday sent out plumes of smoke across busy Highway 78.

Firefighters were called around 1:30 p.m. to 9421 U.S. Highway 78 to tend to a smoldering pile of mulch, according to Bianca Bourbeau, spokeswoman for the North Charleston Fire Department.

Crews from C&B, Summerville, Mount Pleasant, St. Andrews, James Island, Caromi, Old Fort, Charleston County Rescue, Low Country Incident Management Team and the American Red Cross also were on scene.

The fire was contained to a large pile of mulch but was difficult to extinguish, Bourbeau said. Firefighters worked to dismantle the pile in order to fully extinguish the fire and were expected to be on the scene for several hours, she said.

Four firefighters were treated for heat-related injuries and released, she said.

Highway 78 was closed in both directions for a while, and one lane remained closed late Thursday night.

Reach Dave Munday at 937-5553.