At least 60 personnel will work through the evening at the site, where a Lincoln Energy Solutions tanker truck carrying 5,000 to 7,000 gallons of flammable ethanol overturned on Sweetwater Road about nine miles south of Edgefield, said Sandy Backensto, the assistant director of Edgefield County Emergency Management.
The driver suffered minor injuries.
Authorities estimated 3,000 gallons of the highly flammable liquid spilled, she said.
A second tanker had to be called to the scene to continue off-loading fuel from the overturned tanker.
The road was blocked, and people were being kept 1,500 feet from the fuel, Backensto said.
Sand dams were built around the leaking truck to contain the fuel, Backensto said.
Fire department personnel from several jurisdictions were working at the site.
Ethanol is a flammable and explosive alcohol used as a gasoline additive.
Personnel were taking great care to avoid igniting volatile fumes from the leaking fuel, Backensto said.
Authorities did not expect the site to be cleared for traffic until this morning or later, she said.