GUANGZHOU, May 20 -- A Chinese sea patrol ship is on its way to help search for 13 missing sailors after a Bolivian-registered sand- carrier capsized in Singapore waters on Wednesday, according to the Guangdong maritime search and rescue center.

The ship "Haixun 31" was on its way to Malaysia to join a sea rescue drill organized by the Association of Southeast Asian Nations (ASEAN) regional forum, when it received an order to immediately rush to the rescue.

The sand-carrier, Oceanline SC208, had capsized 7.5 nautical miles northeast of Pedra Branca in Singapore waters, said the Maritime and Port Authority of Singapore (MPA).

There were 15 crew members onboard at the time of the accident, 14 of whom are Chinese nationals. One person was rescued while 13 others are still unaccounted for.