The marine rescue service has to do a "bit of detective work" after finding an empty 25-person life raft floating 49 nautical miles east of Dunedin, Rescue Co-ordination Centre spokesman Ross Henderson says.
A helicopter crew flew out to investigate a distress signal generated by the liferaft, received at 5.04pm yesterday.
Mr Henderson said the helicopter crew found no sign of "habitation" on the raft, and determined the beacon had been set off automatically rather than manually.
"Probably what's happened is some water's got into the liferaft or the life raft may have turned over because it's got no weight in it."
It was difficult to know how long the raft had been floating around in the Pacific Ocean, he said.
It was not uncommon for boats to lose life rafts in rough seas.
"We've got a bit of detective work in front of us to try and determine exactly where it may have come from."
The raft would probably be brought to shore, Mr Henderson said.
The centre had picked up nothing to indicate anyone was in distress yesterday, Mr Henderson said.
The size of the life raft indicated it had probably come from a large vessel.
