WA Police are trying to make contact with a man who they believe is unwittingly in possession of a live hand grenade.

The man was with other people at Chidlow on Saturday November 12, when two old grenades were found and two men each took a weapon home.

Today, one of the men went to police and the grenade was found to be live.

Australian Defence Force personnel safely removed the explosive from the man's house and it will be destroyed at a later date.

Police said the identity of the man who took the second grenade home was not known, and the grenade is likely to be live and unstable.

They said the man should not touch or move the weapon and is urged to immediately call police.