Authorities blamed thick fog for a 13-vehicle wreck on Florida's Turnpike that killed at least five people Tuesday and included a fire truck and sheriff's cruiser headed to an earlier crash, officials said.

Four others were injured, Osceola County spokeswoman Niki Whisler said. Two had to be airlifted for treatment, including a sheriff's deputy.

Smoke from nearby brush fires, mixed with morning fog, had led to the first wreck, and the Florida Highway Patrol was investigating the second one, said Sgt. Jorge Delahoz.

He said the second crash happened just after 8:30 a.m. when a patch of thick fog quickly appeared on the road. Delahoz said the victims were from three vehicles, one of them a tractor-trailer.

"According to witnesses, the fog rolled in between the two crashes," he said. "Before the smoke cleared from the second crash, it had rolled out."

Officials shut down a 51-mile section of the turnpike after the accident. Parts of the same area had been closed Monday because of brush fire smoke.