U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives agent Steven Gerido said Friday that lab tests confirmed an accelerant was used in the fire early Saturday in Murfreesboro.
The fire engulfed the cab of a dump truck, and authorities found fresh fuel pooled under a second dump truck and some fingerprints near the fuel tank.
The site is the location for a new Islamic Center of Murfreesboro, which has drawn increasingly vehement opposition, including protest marches and some vandalism. One opponent said she received death threats after appearing on "The Daily Show."
A $20,000 reward is being offered to anyone with information leading to an arrest.