EAST FORSYTH — A near head-on collision between an 18-wheeler and large flatbed work truck Monday afternoon shut down Buford Highway (Hwy. 20) in both directions by the Chattahoochee River bridge, authorities said.

According to the Forsyth County Sheriff’s Office, the busy east-west corridor linking Forsyth and Gwinnett counties was closed for about an hour as a hazardous materials unit cleaned up diesel fuel that spilled in the crash.

“The 18-wheeler was leaking some fuel, and hazmat is containing that to make sure that is doesn’t get into the river, as it is close to the river,” said Robin Regan, a spokesman for the sheriff’s office.

The incident worsened congestion in an area where it is thick under normal conditions. That stretch of the highway is also a work zone, with a 35 mph speed limit at all times, as the state Department of Transportation is widening the road to four lanes and replacing the bridge over the river.

As of Tuesday, the exact speeds of the vehicles involved at the time of impact weren’t known, as the incident remains under investigation.

The 2:10 p.m. collision was the result of an attempt by the work truck, an F-350 loaded with construction material, to come to an emergency stop to avoid striking a passenger vehicle while traveling east.

Unable to make the stop, the truck swerved into the westbound lane of traffic, meeting the 18-wheeler almost head-on some 100 feet from the bridge on the Forsyth side, Regan said.

The driver of the F350, a 36-year-old man from Norcross, was found to be at fault, though no charges had been filed as of Tuesday.

He and the 29-year-old Kentucky man driving the tractor-trailer were released from area hospitals after being treated for non-life threatening injuries, Regan said.

Motorists were advised to avoid the area and take alternate routes if possible. No fuel reached the river.

In three separate projects, the Hwy. 20 corridor between Samples Roads in east Forsyth and Peachtree Industrial Boulevard in Gwinnett is being transformed into a four-lane divided road with sidewalks. The entire stretch is projected to be finished by Nov. 30, 2016.

Staff writer Kayla Robins contributed to this report.