Police were last night making arrangements with a mainland businessman to check whether HK$270 million of gold bullion he bought in Africa was genuine after part of the consignment was swapped with metal bars. On Wednesday, Zhao Jingjun, 43, opened part of his shipment in front of his buyer in Hong Kong and discovered the gold had been switched for worthless metal. A senior officer said it would be the city's biggest heist in a decade if it was confirmed that all the gold had been stolen. An initial inquiry showed Zhao purchased 998kg of gold bars from a company in Ghana in mid-April, police said. The consignment, in 14 cases, was escorted by his staff and delivered from Ghana on a chartered flight late last month. "Officers were told that his employee confirmed the cases contained the gold before it was loaded onto the chartered flight in Ghana," a police source said. The source said the employee left Hong Kong after the consignment was handed to the staff of a logistics company at Chek Lap Kok airport. It was then couriered to a Tsuen Wan warehouse. The businessman arrived from Hebei province on Monday and checked into the Kowloon Shangri-La hotel in Tsim Sha Tsui. On Wednesday, he had five of the cases couriered to his buyer's Hung Hom office. "When he opened the boxes, he found they were filled with metal bars instead of gold bullion," the source said. "He told officers the cases appeared to have been tampered with." Police received a report from Zhao on Wednesday night when he returned to his hotel room. He went to Tsim Sha Tsui police station yesterday with documents proving he bought the bullion in Ghana and that it was delivered to Hong Kong. A police investigator said: "We don't rule out the possibility that the gold bullion may have been switched for metal bars before being delivered to Hong Kong." Zhao has reportedly made several such transactions. His business activities include the purchase of iron ore from Australia, Africa and South America. Four years ago, 265 gold bars were taken from a Yuen Long company. Police arrested three men and recovered most of the HK$90 million in bullion stolen.