Supporters from across America have called to give encouragement to a suburban Nashville mosque where a fire was the latest setback for a planned new building, officials said Sunday.

Authorities told the centre that four pieces of heavy construction equipment on the site were doused with an accelerant and one set ablaze, said Camie Ayash, spokeswoman for the Islamic Center of Murfreesboro. Federal investigators have not ruled it arson, saying only that the fire was being probed and asked the public to call in tips. Earlier, Ayash said that gasoline was poured on the equipment but later backed off that statement.

"No threats, not at all," since the fire, Ayash told The Associated Press. "We've had a tremendous amount of calls of support."

American Muslim leaders say the furor over the building of a mosque near the ground zero World Trade Center site in New York City has emboldened opposition groups to resist new mosques elsewhere.

Some say they oppose them because of infrastructure and traffic problems. Others have implied that the mosque would be a haven for terrorists.

The Islamic Center of Murfreesboro's planned expansion has drawn increasingly vehement opposition from the community in recent weeks. The proposed centre on 15 acres (6 hectares) would serve some 250 families.

Digging had begun at the site where a sign that marks it as the future Islamic Center of Murfreesboro has been vandalized twice in the past several months. But Ayash said the fire "makes everybody really on edge."

Ayash said Islamic Center officials were contacted by the sheriff's department around 4 a.m. Saturday. Someone walking by reported the fire about 1:30 a.m.

Rutherford County resident Kevin Fisher has led protests against the mosque, complaining of zoning issues, parking, traffic and a lack of transparency in the county's planning approval process. He issued a statement Saturday to the Daily News Journal of Murfreesboro.

"We in this community believe strongly in the rule of law, and choose to settle our disagreements through peaceful deliberations and discussion, not vigilantism. ... We who stand in opposition to this mosque have made our concerns known through proper legal channels and have conducted ourselves with dignity, respect and out of a spirit of love for our community, and we will continue to do so."