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. It was not immediately clear what caused the collision, which occurred about 2:10 p.m. some 100 feet from the bridge on Forsyth side. It remains under investigation. Regan said one of the drivers was injured, but had been taken to an area hospital in stable condition. 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.