MIRI, MALAYSIA (THE STAR/ASIA NEWS NETWORK) - Five search-and-rescue teams are combing the dark and treacherous underground river of the Deer Cave in Mulu National Park on Sunday (July 14) morning.

The rescue teams, comprising the Sarawak Fire and Rescue Department, police and local natives, ventured into the deepest parts of the enormous cave to search for missing local native tour guide Roviezal Robin, 20.

Mr Robin and Dutch tourist Peter Hans Hoverkamp, 66, were swept away by flash floods inside the Deer Cave at about 6pm last Friday.

Mr Hoverkamp was found drowned at 7am on Saturday.

The department, known as Bomba Sarawak, in its latest updates this morning, said the five teams are searching the entire route of the river snaking through the Deer Cave.

"The teams are carrying out surface and underwater search, in the tunnels and also along the river tributaries outside the cave.

"The teams are also searching the narrow passages inside the cave," said Bomba Sarawak.

The Deer Cave is one of the largest caves in the Mulu National Park.

Mulu is located about 200km inland from Miri city.