MUAR, Malaysia, March 25 (Xinhua) -- The death toll from a capsized dredger off the southern Malaysian state of Johor in the Mallaca Strait has risen to 4, as rescuers decided to terminate diving operations but expand surface search on Sunday morning.

Sanifah bin Yusof, deputy director of the Malaysian Maritime Enforcement Agency Southern Region, said diving operation has been stopped due to the fact that "all areas have been checked multiple times and there are no more results."

He said, however, search and rescue on sea surface and in the air, involving ships and helicopters from multiple agencies including the navy and marine police, will continue, and Indonesian authorities have also been notified to solicit their assistance if needed.

Search area has been expanded to 360 square nautical miles surrounding the capsized location, he added.

Up until now, five crew members of "JBB Rong Chang 8," a Dominican-registered, Chinese-owned ship, have been saved, and the Chinese embassy in Malaysia has confirmed that three of the deceased are Chinese citizens.

Liu Konggan, chief engineer of the ship who was saved more than 50 hours after the incident, told Xinhua that in complete darkness, he used a metal plank to knock on the ship body to get the attention of rescuers. The knocking sound has been considered as a key indicator of survivors by rescuers.

Liu said sea water was almost about to submerge him then.

Liu was saved along with a sailor named Liang Puzeng. They both sustained minor concussions and bruise from the incident, but were gradually recovering, according to Muar hospital staff.

Liu said they did not eat or drink water since being trapped, but were forced to sip the sea water several times.

The cause of the incident is still under investigation.