I-75 near Ringgold, Ga., will remain closed for most of the day and possibly until Friday after fog caused a massive pileup, killing at least four people.

There have been conflicting published reports from the scene. Some say at least 20 tractor-trailers were included in a pileup of as many as 125 vehicles on the interstate about 12 miles southeast of Chattanooga, Tenn. The accident happened shortly before 8 a.m. on the northbound side of the interstate; heavy fog had cut visibility down to about 25 feet. I-75 was closed in both directions, creating a 12-mile backup of northbound traffic.
Earlier reports said as many as 10 people were killed, but officials later revised the figure to five, then four.
"There were vehicles on top of vehicles," one witness told United Press International. "I see one vehicle between two tractor-trailers. You can't even tell what kind of vehicle it is."
About three dozen people were injured in the accident and those with serious injuries were taken to various local hospitals.
The preliminary investigation has determined that two tractor-trailers made contact, with one going across the median, hitting several vehicles traveling in the opposite direction.
Police told the Associated Press they do not expect any charges to be filed against the drivers, saying the accident was due to foggy conditions.
The crash happened about 40 miles away from the location of a similar pileup in Tennessee in 1990. About 100 vehicles were involved, leaving 12 people dead and 42 injured.
That accident prompted officials to put in place an extensive fog warning system recommended by the National Transportation Safety Board and better markings on the roadway itself.