Police had to evacuate four homes in the Ballycolman area of Strabane when a suspected firearm was recovered during a search operation.
The army bomb disposal team was called to the scene, which was sealed off from 9.20am to 2pm on Saturday.
The device was taken away for further examination.
Strabane SDLP Councillor Patsy Kelly condemned the incident in the large, built up area.
“This is completely unacceptable and I had hoped that we had moved on from a time when such terrible actions would be visited upon the community,” said Mr Kelly.
“These actions serve no one and no purpose.
“I am especially concerned for the families who have had to be moved from their homes and the distress and disturbance caused to them as a result.
“I would appeal for anyone with any information on this incident to contact the PSNI.”