Tasmanian police investigating a suspected double murder south of Hobart expect to interview a man over the incident later today.

Police found the bodies of a couple aged in their 60s at the Mountain River house early this morning. A 27-year-old man was arrested at the scene. He is believed to be related to one of the victims.Police believe the couple was bludgeoned to death.A possible weapon has been found at the site but police will not say if it was used in the incident.Inspector Ian Lindsay says enquiries are being made to confirm their identities.