KOTA KINABALU, Malaysia - Malaysia has expanded the search area for the six people remained missing after their boat sank off Sabah state on North Borneo, with neighboring Brunei also joining the search effort, authorities said Monday.

Malaysian Maritime Enforcement Agency said the search and rescue operations on Monday were launched at 7:00 a.m. local time with the search area expanded to 1500 square nautical miles into waters in Brunei.

Vessels from the Maritime Enforcement Agency, Malaysian Navy and a C-130 aircraft from Malaysian air force are among the assets deployed for the search. Brunei is also sending a helicopter for the operations, according to the Maritime Enforcement Agency.

So far 20 Chinese tourists and 2 crew members have been rescued, three dead and six people remained missing. The surviving Chinese tourists were sent back to Kota Kinabalu, the state capital of Sabah early Monday.

Their boat went missing on Saturday when travelling from Kota Kinabalu to Pulau Mengalum, a popular tourist island, 60 km west to Kota Kinabalu. A total of 31 people were on board, including 28 tourists from China and three crew members.