The mystery deepens as to just what was found on a mid-Canterbury farm following yesterday's sonic boom that was heard across the region.

This morning scientists at the National Radiation Laboratory in Christchurch tested a piece of material that is the size of a person's palm and looks like a rock.

Lab General Manager Jim Turnbull says the material is not radioactive, which means it is not a nuclear device from a space craft and he also doubts it is a meteorite as it is too light.

He says, however, it still may have something to do with yesterday's sonic boom and says it could be a fragment of space junk.

Jim Turnbull says the object may be returned to the owner or be handed over to geologists or staff at the University of Canterbury.