A series of fires along a popular walking and cycling trail in Contra Costa County have been determined to be intentionally set, according to fire officials. A spokesman with Contra Costa County Fire Protection District confirmed that arson was the cause of multiple fires along the Iron Horse Regional Trail Monday afternoon. Crews responded to the fires reported shortly before 3 p.m. that dotted the trail between the cities of Pleasant Hill and Concord between Sherman and Brookview drives. The fire district wrote on Twitter shortly after 3:15 p.m. that the fires had been contained and nearby structures were no longer threatened. People are asked to avoid the Iron Horse trail and surface streets in the area while crews mop up and do other work in the area Monday afternoon. The Iron Horse Regional Trail spans 32 miles from Concord south to Pleasanton, according to the East Bay Regional Park District.