KUALA LUMPUR: Twenty-five, mostly Chinese tourists, were rescued Sunday after spending more than a day drifting in Malaysian waters after their boat sank, officials said.

Six of the 31 people on board were still missing Sunday evening, Shahidan Kassim, a minister in the prime minister's department, told reporters in Sabah state.

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The boat's captain and a crew member were spotted by a military plane and rescued, Shahidan said. Fishermen later rescued a group of 10 people and another group of eight, while a tugboat found a group of five, he said.

Shahidan said search efforts will be intensified, including using surveillance planes that see in the dark.

Twenty-three of the recovered are Chinese as are five of the six still missing, Sabah Police Commissioner Ramli Din tweeted.

An official with the Malaysia Maritime Enforcement Agency said the rescuers were being hindered by high winds and choppy waters. The official declined to be named because he isn't authorized to speak to the media.

The search area is about 400 square nautical miles (nearly 1,400 square kilometers) of the South China Sea.

The captain and a crew member were found between the island of Pulau Tiga and an offshore oil drilling platform, Malaysia's The Star Online reported. The boat had left Kota Kinabalu in Sabah state on Saturday morning on its way to Pulau Mengalum, an island about 60 kilometers (38 miles) west.

Arwin Musbir, the captain of another boat that left for Pulau Mengalum at the same time, told the New Straits Times newspaper that he was following the missing boat but lost sight of it shortly after they left. He said he realized it had gone missing only after he arrived at the island.

Many Chinese travel abroad during the Lunar New Year holiday, which began Saturday.