Photo provided by Maritime and Port Authority of Singapore on Sept 13, 2017 shows four tug boats moving the partially submerged sand dredger to an area near Singapore's Pulau Senang. [Photo/Xinhua]

SINGAPORE - Four Chinese nationals and a Malaysian went missing after a Dominican-registered sand dredger collided with an Indonesian-registered tanker in Singaporean waters early Wednesday morning.

The Maritime and Port Authority of Singapore said in a statement that it was notified of the collision at about 12:40 am Singapore time.

The sand dredger with 11 Chinese crew members and one Malaysian on board was transiting the westbound lane while the tanker was joining the eastbound lane of the Traffic Separation Scheme in Singapore Strait when the incident occurred, the statement added.

After the collision, seven Chinese nationals aboard the dredger were rescued by the Singapore Police Coast Guard and transferred to the Singapore General Hospital, while the four other Chinese and one Malaysian crew member are still missing.

Search and rescue operations led by the MPA are still going on.

Several petrol crafts have been deployed by the MPA, Singapore Navy, Singapore Civil Defence Force and PCG to search for the missing. A Super Puma helicopter from the Singapore Air Force was also mobilized as from 7 am local time.

The MPA said that it is investigating the incident and there is no disruption to shipping traffic in the Singapore Strait.

According to an official with the Chinese Embassy in Singapore, one of the seven Chinese crew members sent to hospital has a rib fracture and the conditions of the other six are fine.