SINGAPORE, Dec. 20 -- Five of the 11 crew members of a barge that capsized in Singapore waters on Thursday were still missing, the Maritime and Port Authority of Singapore said Friday.

All the crew members onboard the Bolivia-flagged Heng Long 168 are Chinese nationals, the authority said.

The authority received report Thursday that a life raft with people onboard had been sighted southwest of Horsburgh Lighthouse in the Straits of Singapore. Six of the 11 crew members were subsequently rescued by a Police Coast Guard patrol.

The search and rescue operations involving aerial and surface searches are still ongoing. Commercial divers were also called to help with the operation.

Investigation into the incident is still underway.