Malaysian rescue ships and helicopters were encountering strong winds and choppy waters Sunday while searching for 31 people, including around 20 Chinese tourists, whose boat went missing near an eastern Malaysian city, media reported.

The Chinese Consulate General in Kota Kinabalu in the Malaysian state of Sabah said the boat lost contact after leaving Kota Kinabalu on Saturday morning, according to the official Xinhua News Agency said. It was bound for Pulau Mengalum, an island about 60 kilometers (38 miles) west of the city.

The report cited the Malaysian Maritime Enforcement Agency as saying there were 28 Chinese tourists on board. But the Chinese Consulate could only confirm the passport details of 18 Chinese citizens, Xinhua said.

Malaysia deployed search and rescue ships and helicopters after receiving a call Saturday night about the boat's disappearance, Xinhua reported. Calls to the Chinese Consulate rang unanswered Sunday.

Authorities are searching a section of the South China Sea of about 400 square nautical miles (nearly 1,400 square kilometers), according to The Star daily in Malaysia. They are contending with strong winds and choppy waters.

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.