The westbound lanes of Monroe Street at Whiteford Drive in Sylvania Township are closed because of a gas-line break, police dispatchers said.
A natural-gas odor was reported to police at 9:24 a.m.
Police and Columbia Gas crews were on scene at 10 a.m.
Several buildings in the area were evacuated although it was not clear if there was any immediate danger, officials said.
Police did not have an estimated time for when repairs might be completed and when lane restrictions would be lifted.