[SYDNEY] China's north-eastern port of Qingdao has halted shipments of aluminium and copper due to an investigation by the authorities, causing concern among bankers and trade houses financing the metals, trading and warehousing sources said on Monday.

Port authorities could not immediately be reached for comment. China had a public holiday on Monday. "We were told we can't ship any material out while they do this investigation," a source at a trading house said.

The port of Qingdao is China's third-largest foreign trade port and the world's seventh-largest port, trading with 700 ports in more than 180 countries, according to its website.