Rescuers Monday expanded their search for four Chinese tourists and a crewman whose boat sank in rough seas off Malaysia, as police detained the skipper, another crewman and the boat owner for suspected negligence.

The owner had breached procedures, including overloading the boat, Sabah state Police Commissioner Ramli Din was quoted as saying by national news agency Bernama.

“Police will also investigate whether negligence led to the deaths of the tourists,” Ramli said.

This picture taken on early January 30, 2017 shows medics transporting a survivor at a jetty in Kota Kinabalu in the Malaysian Borneo state of Sabah after a tourist catamaran sank on January 28. Photo: AFP/Stringer.

The sinking of the catamaran off Sabah on Borneo island on Saturday, the first day of the Lunar New Year holiday, sparked a major air and sea search.

Twenty exhausted Chinese tourists survived hours in the water thanks to their life jackets and by clinging desperately to objects from the boat, but three other tourists died.

The skipper and another crew member were earlier rescued off a nearby island.

Initially, authorities said 28 Chinese tourists were on board the ill-fated vessel. But late Monday Malaysian officials said one Chinese had failed to show up for the trip.

The search area has been further expanded from 1,500 to 2,400 nautical square miles, Awil Kamsari, a spokesman for the Malaysian Maritime Enforcement Agency, told AFP.

Awil said the search was expected to continue through the night despite adverse weather.

Malaysian navy chief Ahmad Kamarulzaman Ahmad Badaruddin told AFP that more assets have been deployed.

Part of the search area falls in Brunei’s waters and the sultanate’s navy is assisting, he said.

“It’s not going to be easy as time is critical. The longer it takes, the lower the probability of finding them,” Ahmad said, adding the sea was still very rough.

“But we cannot lose hope and must continue.”

The search was postponed due to rough seas on Sunday night but resumed Monday morning.

Malaysian Prime Minister Najib Razak said on his Facebook page he wanted a “thorough investigation” into the incident.

China’s foreign ministry also urged “a fair and objective investigation to find out the truth in the accident as soon as possible”.

The boat with 27 tourists and three crew aboard had left the Sabah state capital Kota Kinabalu for Pulau Mengalum, an island known for its pristine beaches and dive sites.

The boat owner reported it missing on Saturday evening.

The skipper said the boat had “broken” and sank after being hit by big waves.

The traumatised and exhausted survivors were taken to Queen Elizabeth Hospital in Kota Kinabalu.

A Malaysian official there told AFP they “looked shocked” and some “could not walk and looked very tired” as they were taken to hospital.

He said they survived because of their life jackets and by clinging on to objects from the boat.

State Tourism, Culture and Environment Assistant Minister Pang Yuk Ming said authorities were checking whether the catamaran had sailed from a jetty in Kota Kinabalu that was not intended for tourist trips to nearby islands.

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