Bomb disposal experts were called after a man found an old hand grenade while gardening at his home in Higham Road, Rushden, on Wednesday afternoon (June 26).
Police were called to the man’s home at about 3.30pm, when he found the device, thought to date from World War One.
A spokesman for the Northamptonshire force said they contacted the RAF’s Explosive Ordnance Disposal team and alerted neighbours to stay away from their windows to avoid the risk of injury.
He added: “Officers were not sure if the device had been made safe or not, so it was decided to contact the experts.
“The RAF team carried out a controlled explosion.
“We did not have to evacuate neighbours, rather we asked them to keep clear of windows, just in case anything went wrong.”
The bomb disposal team left the scene at about 7.30pm.