A locked metal safe with a damaged faceplate was turned in to the Alexandra police station by a person who found it between the Clutha River and State Highway 8 in the Cromwell Gorge.
Sergeant Ian Kerrisk, of Alexandra, said the safe was found at the Alexandra end of the gorge, where the road verge met the river bank.
Sgt Kerrisk said all police had searched their files for any reports of missing or stolen safes, but found nothing.
"It's unusual to find a safe abandoned like that, but there may be a perfectly valid reason for it," he said.
The safe was found on November 1, and police were not sure whether it was domestic or commercial. It appeared to have a broken combination handle as well as a keyhole and some lights.
Police said it weighed about 12kg, and measured 25cm wide, 35cm long and 25cm deep.
They were not sure whether it contained property or was empty.
