The chain-reaction accidents around 8:10 a.m. Wednesday killed four people and sent nine others to a hospital, authorities said.
A trooper was out all night checking for lingering smoke from controlled burns in the area, Georgia State Patrol operator Terri Graffagnino told The Telegraph newspaper of Macon. The trooper has been patrolling overnight from mile markers 36 to 54, where fog routinely gets thick, she said.
Dense fog was reported Wednesday morning in the region, where visibility was only a quarter-mile or less, meteorologists said.
Motorists also reported smoke across the highway, Georgia State Patrol Capt. Kirk McGlamery said.
The Georgia Forestry Commission issued a permit Tuesday morning for underbrush to be burned on 75 acres in Montrose, just north of the interstate.
State firefighters responded to a wildfire in the area later Tuesday, around 5:20 p.m., the Telegraph reported.
It's unclear whether the wildfire was spawned by the controlled burn, said Frank Sorrells, of the forestry commission. He said it's not uncommon for smoke to linger long after fires are put out.