Firefighters from Walnut responded to a call about a semi tractor-trailer fire on Interstate 80 westbound Tuesday afternoon, at the Walnut exit. Dispatch reports at around 2:45-p.m. indicated flames were coming from the engine compartment. The trailer was said to have been carrying a highly flammable fuel. The truck driver managed to get most of the fire out with his on-board extinguisher before firefighters arrived. They weren’t on the scene for very long, and no injuries were reported. The cause of the fire was under investigation.