Seven bodies were recovered after a cargo loaded with 3,000 tonnes of sand sank on the Bohai Sea off north China's Hebei Province Saturday, local authorities said.

The vessel from the coastal city of Penglai in Shandong Province sank at about 5 am. The number of the crew members was unknown, according to the Huanghua Maritime Safety Administration.

The maritime search and rescue center of Cangzhou City received a message asking for help from the vessel at about 5:15 am, but lost contact with it from then on.

The center was organizing ships and helicopters to conduct the rescue, but the efforts were hindered by strong wind and waves up to four meters, officials said.