A grass fire along I-75 had all northbound lanes blocked south of Atlanta Saturday afternoon.

A tractor-trailer hauling bales of cotton caught fire near the Locust Grove exit just before 1:30 p.m., and the flames spread to the grass along the interstate, according to Doug Turnbull in the AM750 and 95.5FM News/Talk Traffic Center.

Turnbull said all northbound lanes remained blocked at 4:45 p.m., with the state Department of Transportation predicting it would be at least 6 p.m. before the interstate reopened.

Northbound traffic was backed up about 13 miles, Turnbull said.