Chinese archaeologists yesterday began a third round of excavation work on the Nan'ao-1, an ancient merchant vessel that sank about 500 years ago off the coast of Guangdong Province.
Security staff will watch over work on the wreck, which has fallen victim to illegal smuggling in the past.
Archeologists sent by national and provincial cultural relics departments have already carried out underwater excavation of the ship twice since 2009, recovering more than 20,000 antique pieces, including porcelain and bronze coins.
A spokesman for the Guangdong provincial bureau of cultural relics said archeologists will salvage all porcelain items from the ship during the third round, which is expected to last for three months.
The team plans to install a giant iron mantle over the wreck to protect the relic, which was buried in silt 27 meters under water when it was found by fishermen in May 2007.