Residents from 10 homes were evacuated after the discovery of a suspicious device in Walton-le-Dale.
Contractors digging a hole on a building site in Walnutwood unearthed what appeared to be a wartime shell and police immediately threw a tight cordon around the area.
Bomb disposal officers were called out to examine the object and residents were taken to a temporary shelter as a precaution.
More than three hours later the Army announced the shell was a spent mortar which was taken away and the cordon lifted.
A police spokesman said: “We were called in at 2pm after a contractor working on a building site in Walnutwood, Walton-le-Dale, discovered a suspicious device while he was digging a hole.
“A cordon was set up around the area and 10 homes were evacuated.
“Bomb disposal experts were called in to look at the object and a temporary shelter was set up for the people who had left their homes.
“But when the Army examined it they found it was some kind of mortar which had already been detonated. So it wasn’t posing any danger.”
A Lancashire Fire service spokesman said: “Lancashire Fire and Rescue Service’s air support unit attended a report of a suspected mortar found on Walnutwood Avenue in Bamber Bridge. The drone was used to take images of the mortar before an explosive ordnance disposal team confirmed that the item was a spent device and it was removed.”
After more than three hours the householders were allowed back into their homes.
A spokesperson for Persimmon Homes said: “Landscape work was being carried out at our Pear Tree Gardens development at Walton-le-Dale when a suspicious object was found.
“We immediately notified the police who dealt with the matter.”