The origins of the huge barnacle-covered cylinder discovered on Green Head Beach in Western Australia left many stumped when it appeared earlier this month, although initial theories leaned towards it being "space junk".

But the Australian Space Agency made a more concrete conclusion, saying the object was "most likely" debris from an "expended third-stage of a Polar Satellite Launch Vehicle".

The medium-lift launch vehicle is operated by the Indian Space Research Organisation. The third stage of the vehicle is jettisoned at an altitude of 264 miles.

The gold-coloured canister measuring around 2.5 metres long and 2.5 metres wide is now being kept in storage.

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Previously the object was under guard by police, although it was quickly determined to be safe and not a risk to the community.

Officials from both India and Australia are working together to "provide further confirmation to determine next steps, including considering obligations under the United Nations space treaties", the Australian Space Agency said.

Local resident Garth Griffiths said a neighbour alerted him to the strange find two weeks ago.

"A local lady and her partner discovered it just floating on the edge of the water and dragged it out with their four-wheel drive," he told ABC News.

"There were barnacles and marine life growing on it."

Australia is no stranger to orbital remains mysteriously appearing in random places, with space debris from Elon Musk's SpaceX craft crashing into a New South Wales farm last year.