Two explosions caused minor exterior damage at a mosque complex about two hours after evening prayers, and federal agents joined the investigation.

No injuries were reported and police hadn't found any witnesses to the Tuesday night explosions at the Islamic Association of Cincinnati mosque, police Capt. Gene Hamann said.

The FBI and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives were involved in the case, joining Cincinnati and State Highway Patrol state investigators, FBI Special agent Mike Brooks said.

Brooks confirmed Wednesday morning there were two explosions, one at each of two adjoining buildings owned by the association.

"As of right now, we can't make any comment on the size or the type of explosive," Brooks said. He also said authorities wouldn't speculate on why the buildings, both used as mosques, were targeted.

One explosion damaged an overhead glass panel in a front entryway at the mosque, and the other damaged a door on a porch at an adjacent house.

There was no immediate comment Wednesday from the Islamic Association of Cincinnati, where a telephone rang busy.

The mosque is about a mile from the University of Cincinnati campus and near several churches and Hebrew Union College.

About 300 to 500 people worship at the mosque on a typical Friday, said Karen Dabdoub, director of the Council on American-Islamic Relations in Cincinnati.

"This is very disturbing," she said. "And not only for this mosque and our community, but for the Islamic community in and around greater Cincinnati."