Two panamax bulkers controlled by a Ningbo shipowner have been idle since the beginning of June in what observers believe is a complication from China's controversial sea sand trade.

The Ningbo Hezhong Shipping vessels have stood at anchor fully laden since the first week of June.

Both ships had just proceeded from the shallow sand banks of the Taiwan Strait, which they had visited with AIS signals switched off before proceeding to the intended discharge port of Guangzhou.