The Georgia State Patrol is investigating why a tanker truck wrecked Wednesday morning on Interstate 985 at the Plainview Road overpass in South Hall County.

The wreck just before 6 a.m. killed the driver and shut down the roadway in both directions for much of the morning.

Georgia State Patrol Trooper Jonathan Folendore identified the driver as Brian Zegarzewski, 49, of Fletcher, N.C. Zegarzewski worked for Carolina Ready Mix and Builder Supply, according to the state patrol.

The driver, hauling a full load of dry concrete, was traveling north on I-985, when, “for unknown reasons … (he)  left the roadway, hit both guardrails (lining the road) and eventually hit one of the support columns” on the overpass, said State Patrol Capt. Allen Marlowe, Troop B commander.

Concrete spilled across the northbound lanes, and the truck driver was thrown from the vehicle, Marlowe said.

The Hall County Sheriff’s Office reported the driver was dead when they arrived.

Speed is a possible factor in the wreck. A witness reported being passed south of the accident scene by the truck, according to the state patrol. The witness said he was going about 75 mph when he was passed; the speed limit is 70 mph.

“He felt like the truck was speeding because the truck passed him,” Marlowe said.

“We’re looking at all different angles,” he said as to cause.

The wreck initially shut down southbound and northbound lanes between Spout Springs Road in Flowery Branch and Exit 17 in Oakwood — a 5-mile stretch.

Traffic was rerouted on roads around the area, including Atlanta Highway/Ga. 13, Thurmon Tanner Parkway and Hog Mountain Road, creating a rush-hour mess.

Hall County firefighters found the truck “50 percent involved with fire” upon arrival.

Chris Avenue resident Curtis Pirkle said the crash “sounded like a bomb went off” and shook his whole house, awakening his family.

Helicopters were soon flying around, and he left the house to find out what was going on, discovering the truck on fire, Pirkle said.

Crews eventually were able to put out the fire and control a fuel leak, according to the fire department.

Also responding to the scene were Georgia Department of Transportation inspectors.

Oakwood Public Works Supervisor Jason Spencer said the bridge shifted and he showed a seam in the structure that had separated about an inch.

Sheriff’s Office spokeswoman Nicole Bailes said an overturned box truck near Exit 8 and multiple fender benders caused additional problems earlier in the morning.

“It has become such a traffic nightmare this morning,” she said at about 8 a.m.

The wreck also delayed school buses in the West Hall, Johnson and Flowery Branch clusters, according to Hall County Schools.