Chinese customs officials have finally given clearance to Rio Tinto to ship out its copper concentrate products from its massive Oyu Tolgoi mine to target customers in China.

Turquoise Hill Resources Ltd, Rio Tinto's Canadian-listed subsidiary which owns Oyu Tolgoi by 66 per cent, on Monday said Chinese customs officials have allowed the entry of some US$425 million of mainly copper and gold concentrate into mainland China.

"Oyu Tolgoi's customers have been engaged with Chinese customs officials and have received the necessary approvals allowing them to collect purchased concentrate," Turquoise Hill said in a statement, noting that on Saturday, a convoy carrying concentrate left its warehouse on the Chinese border.

The company said the approval was important otherwise the mine's customers won't be able to withdraw the copper concentrate they have bought from warehouses across the Mongolian-Chinese border. Turquoise Hill won't also be able to efficiently and effectively record revenue until all customers had successfully received their product orders.

"The withdrawal of concentrate from the warehouse by customers is expected to ramp up quickly," said the Toronto-listed company in a statement.

Regardless of the customs impasse, Oyu Tolgoi continued with its production. Turquoise Hill said it expects concentrate shipments to align with production rates by year end.

According to Britain's Financial Times, the customs impasse came about because the border crossing at China that is supposed to accept the concentrate can only accommodate trade between Chinese and Mongolian companies.

Located about 50 miles or 80 kilometers north of Mongolia's border with China, the Oyu Tolgoi copper and gold project was touted to become one of the world's five biggest copper mines. It is expected to produce an average of more than 544,000 tonnes of copper, 650,000 ounces of gold, and 3 million ounces of silver a year over the next 10 years.

The open pit mine contains deposits estimated at 81.3 billion pound of copper and 46.4 million ounces of gold.