Mining giant BHP Billiton has sold off 800 accommodation units that were ordered for the Olympic Dam expansion, but the new owner remains a mystery.

The company had spent more than $1billion on preparation work for the expansion project before it was put on hold.

The Hiltaba worker’s camp - which would have housed 10,000 people - had already started taking shape, but since the expansion has been put on hold, 800 transportable accommodation units, probably bought from China, have been sold at an Adelaide auction.

The two, three and four-bedroom housing blocks come fully decked out like portable hotel-rooms.

“They’ve got air conditioning, reverse cycle, water heating, beds, cabinets, lock safe,” said Matthew Long from Manheim Auctions, another auction house.

Auctioneers Mason Grey Strange will not reveal who bought the mining camp or how much they paid, but an expert has put an approximate value on what the village is worth.

“I estimate, looking at the details, about $7.8million,” Mr Long told 7News.

BHP says more than 900 units have already been installed, but the other 800 were no longer needed.

It is estimated BHP lost at least 20pc of the purchase price when it sold the surplus transportable accommodation units.