Relic protection authorities and border police have been put on the alert for thieves eyeing the sunken Nanhai No 2 ship, following the recent salvage of a similarly treasure-laden ancient vessel on Saturday.

Experts with the Guangdong provincial relic protection authority said the 400-year-old Nanhai No 2, which sank off the South China Coast during the Ming Dynasty period (1368-1644) and was discovered by two fishing boats in May this year, carried nearly 10,000 pieces of porcelain.

The waters where the shipwreck lies is thought to be shallow compared with that of the Nanhai No 1 - lifted on Saturday - and therefore easier for illegal salvaging.