The Australian authorities said Thursday that they were helping Papua New Guinea with rescue efforts for a passenger boat that was reported to have sunk with as many as 350 people on board.

The Australian Maritime Safety Authority said it had detected a distress signal from the vessel, the Rabaul Queen, on Thursday morning.

The boat is thought to have gone down about 16 kilometers off the east coast of the Papua New Guinea mainland while ferrying passengers from the town of Kimbe on New Britain Island, the Australian agency said.