The Associated Press

AP Photo/Reinhold Matay Dense smoke left from a brush fire and fog caused an early morning multi-vehicle pileup that closed Interstate 4 near Lakeland, Fla., Wednesday.

LAKELAND, Fla. — About 70 vehicles crashed on an interstate blanketed by fog and smoke from a brush fire early Wednesday, killing four people, authorities said.

Nearly 15 miles of Interstate 4 between Tampa and Orlando was closed by several crashes, including the pileup. Aerial footage in the early morning showed the soupy mix of fog and smoke covering the landscape for miles and giving the sky an eerie golden color.

The poor visibility forced rescuers to walk along the closed interstate checking individual vehicles for injured motorists, Florida Highway Patrol Trooper Larry Coggins said. The conditions cleared in late morning, showing mangled, charred trucks and cars pinned underneath some tractor-trailers.

Workers were still trying to rescue one man pinned beneath an overturned truck. There is no estimate on when I-4, the main east-west artery for central Florida, will reopen.

Coggins said 38 people were injured, five seriously.

Tractor-trailers overturned on the roadway, including a tanker. At least six of them burned completely.

"Everything came to a halt," Robert Ellison, who was driving east on the highway about 6 a.m., told The Tampa Tribune and WFLA-TV. "You can't see your hand in front of your face."

One of the first people involved in the accident was a sheriff's deputy, Polk County Sheriff Grady Judd said. The deputy told Judd that conditions on the road worsened suddenly. "'It was clear, it was a little foggy, then it was total darkness,'" Judd recounted the deputy saying.

The sheriff said the deputy was shaken up but helped move people to safety as vehicles continued to crash _ the sounds of metal grinding and gnashing in the darkness.

The Florida Highway Patrol is investigating the crash and the role of smoke from the fire, which started as a controlled burn and grew out of control.

The fog was a contributing factor to the crashes, Coggins said, but he downplayed the smoke as a cause, saying deputies who were patrolling the area earlier Wednesday morning reported smoke was not an issue.

Since Tuesday, the brush fire has charred 400 acres. It is burning roughly half a mile from the highway and is 90 percent contained, Division of Forestry spokeswoman Chris Kintner said.

Forestry workers notified the highway patrol that smoke from the blaze could mix with fog, she said. Warnings signs were also placed on the interstate, but Kintner said she didn't know whether the signs were lit.