The army bomb squad was called to a village close to Sheffield after an old grenade was found.
The grenade was discovered off Main Road, Unstone, at 12.25pm yesterday.
It was found about 150 metres away from the road in some trees.
A Derbyshire Police spokeswoman said: "The army bomb squad arrived shortly after 2pm and carried out a controlled explosion.
"Our incident doesn’t record whether or not it was live."
Luke Junior heard the grenade being blown up.
He said: "We were there when it was destroyed.
"It was blown up by the bomb squad at the back of a car wash. It was really loud."