An explosion went off near a mosque and a house occupied by an Islamic association late Tuesday, authorities said. No injuries were reported.
Police closed nearby streets and investigators combed the area with bomb-sniffing dogs.
NBC News affiliate WLWT said a small pipe bomb may have been found at the mosque, but the report could not be confirmed.
"This is very disturbing," said Karen Daboub, director of the Council on American-Islamic Relations in Cincinnati. "And not only for this mosque and our community, but for the Islamic community in and around Greater Cincinnati."
The mosque closed about 8 p.m. Tuesday. Police received a call about 10:45 p.m. from someone who heard an explosion.
The explosion occurred near a two-story brick house owned by the Islamic Association of Cincinnati and an attached worship center that opened about two years ago.
A message seeking comment was left for an FBI spokesman. The phone number for the mosque was busy.