Qingdao Port China
China's Qingdao Port, which is the subject of a fraud investigation by the authorities Reuters

Chinese police are investigating the death of an official at Qingdao port, which is at the centre of a major fraud probe.

According to a report in China's state-run news agency Xinhua, Qingdao Customs Deputy Commissioner Bian Peiquan died of "unnatural causes" on 5 August. It is not yet known if the death is connected with the on-going fraud investigation.

Qingdao, one of China's largest ports, is under investigation by the authorities over allegations that commodity traders used duplications of warehouse receipts to borrow multiple times on the back of a single cargo of iron ore.

Since coming to power as president of China in 2013, Xi Jinping has sought to root out corruption within the Chinese mega-bureaucracy, state-owned companies and their private counterparts.

This is to improve the integrity of China's economy, the second biggest in the world and soon to overtake the US in the top spot, and attract more foreign investment.

Since the clampdown there has been a spate of suicides by top Chinese officials.