The police report lists a "bias motivation" in the crime, labeling it "Anti-Islamic (Moslem)."
The sheriff is working with the ATF and the FBI on the case. The federal agencies have so far said there's "no indication" there was religious bias or evidence of a hate crime.
The mosque, which is part of the Islamic Center of Murfreesboro's planned expansion, has been the subject of vandalism, the fire and threats since construction began.
The department is still investigating two incidents of vandalism earlier this summer, in which the sign announcing the community center was spray painted with "not welcome" and then broken. There were no police reports available for those incidents.