Murfreesboro, Tenn. - Federal investigators said Friday that a suspicious fire that damaged construction equipment at the site of a future mosque in Tennessee was arson and offered a $20,000 reward for information leading to an arrest.

The blaze frightened members of the Islamic Center of Murfreesboro, which has found its plans to build a new mosque drawn into a fierce debate surrounding a proposed Islamic community center two blocks from Manhattan's ground zero.

Firefighters had said there was a strong smell of diesel from the fire that engulfed the cab of a dump truck last weekend, and authorities found fresh fuel pooled under a second dump truck, according to an incident report from the Rutherford County Sheriff's Department.

Still, authorities did not officially rule the fire an arson until laboratory tests on samples from the burned dump truck tested positive for accelerants.

The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives and FBI is offering a $20,000 reward to anyone with information leading to an arrest.

"Somebody knows something," ATF agent Steven Gerido said. "The money is a motivator."

FBI agent Keith Moses said the FBI would not decide whether the arson was a hate crime - motivated by someone hoping to intimidate local Muslims - until after suspects are identified and their motives are determined.

The Islamic Center of Murfreesboro has outgrown its current rented space in an industrial park. Members got approval to build a new mosque in May. Since then opposition to the building has made international news, with some opponents saying they fear Muslims want to overthrow the U.S. government.

One mosque leader, Essam Fathy, has speculated that the perpetrator is not from the area and that new attention has been drawn to the Tennessee project by the ground zero dispute. Members of the Murfreesboro mosque say they have lived and worshipped in the community for years and never caused any problems.