An afternoon wreck on I-85 in south Fulton County snarled traffic for hours Friday and left a tractor-trailer driver in critical condition.

Investigators believe the driver of a northbound, white Ford pickup truck lost control and traveled into the path of a tractor-trailer on I-85 northbound after Senoia Road, according to Detective Melissa Parker with Fulton County police. The tractor-trailer couldn’t avoid the pickup, and the collision sent both vehicles towards the shoulder of the roadway, Parker said.

The pickup truck came to a stop, but the tractor-trailer struck the guardrail, traveled up the concrete wall and hit the bridge’s concrete pillar, Parker said. After hitting the bridge, the trailer and cab separated, causing the trailer to flip on its side and the cab to land further down I-85.

The driver and a passenger in the pickup sustained non-life threatening injuries and were transported by ambulance to Grady Memorial Hospital. But a medical helicopter landed on the interstate to transport the tractor-trailer driver to Atlanta Medical Center, according to police. The tractor-trailer driver, whose name was not released, was in critical condition late Friday, Parker said.

The wreck had all northbound lanes of the interstate blocked after Senoia Road at around 4:30 p.m., according to the Georgia Department of Transportation. By 7 p.m., all but one lane had re-opened. The final lane wasn’t expected to open until midnight.

Both Fulton County and Fairburn police were at the scene of the wreck, which scattered debris, including scrap metal, across several lanes.

Those traveling on I-85 northbound Friday afternoon were advised to use Exit 29, Roosevelt Highway, as an alternative route, according to the WSB Traffic Center. Onlooker delays were being reported on the southbound side of I-85, slowing traffic back to I-285.