Police and federal Homeland Security agents were investigating the threat, The (Nashville) Tennessean reported.
The threat was left on the answering machine of the Islamic Center of Murfreesboro about 1 a.m. Monday and discovered Tuesday afternoon, said Officer Kyle Evans, a spokesman for the Murfreesboro Police Department.
The message said a bomb would be placed in the building Sept. 11 and the caller made "derogatory remarks toward the Muslim faith,'' Evans said.
The threat likely will be investigated as a hate crime, Evans said.
"It is most definitely hate-filled speech, but more importantly, it's just meant to intimidate, especially at a time when our nation is grieving and trying to remember 9/11, it is very inappropriate," Evans said.
Police plan to increase patrols around the Islamic Center.