Police assisting in the intervention of a suspected asylum seeker boat off Western Australia's northwest coast have returned to port.
But they have refused to comment on the fate of the boat, or those on board.
The boat, carrying what were believed to be Vietnamese asylum seekers, was spotted by crew members on an oil tanker at first light on Monday morning about 70 kilometres offshore.
Numbers could not be confirmed but those onboard appeared to be in good health, a spokesperson for oil and gas company Modec said.
Water police were called in to help locate the boat and it was understood that an Australian Navy vessel followed later.
Police who returned to the Dampier port overnight would not comment on the operation to intercept the vessel, other than to say the boat was unlikely to dock at the port and that police would have no further involvement.
A spokesperson for Minister for Immigration and Border Protection, Peter Dutton, said the Government did not comment on operational matters.
Almost two years ago to the day an asylum seeker vessel arrived at a floating oil platform 200 kilometres off Dampier with 17 people from Vietnam on board.