Thirty-three Chinese tourists who visited the southern resort island of Jeju in South Korea were still missing on Monday, prompting the local police to say they might want to remain in the country illegally.

Police said that about 1,300 Chinese tourists visited the Jeju Island on Sunday on board the cruise ship Costa Classica. Forty-four of them, including 30 males and 14 females, failed to return to the ferry on time after taking a tour of the island.

Police said they have managed to locate 11 of them.

"As the Chinese tourists found by the police left their passports on board the ship but took their luggage with them, they appear to have entered the country with the intention of staying illegally and getting jobs," an investigator with the Jeju immigration office said on condition of anonymity.

"As soon as we find all of them, we plan to deport them," the investigator added.

An official from the Republic of Korea (ROK) embassy in Beijing, who also wished to remain anonymous, told China Daily on Monday that the 11 Chinese who have been found will be put up in local hotels while police search for the others.

"It's possible to expel these Chinese if it is confirmed they acted intentionally, according to the law of the ROK," he said.

Checks have been intensified at airports, ports and hotels on the island.

Chinese passport holders have a 30-day tourist visa on arrival if they take direct flights or a cruise to Jeju, but South Korean police can detain them if they fail to follow the agenda they have arranged with Chinese travel agencies, according to an official, surnamed Zhu, from the Korea Tourism Organization's Beijing office.

"Traveling with a group or by oneself is different," said Ding Zhenyi, who works at the travel agency SAL Tour and has experience of cruises to Jeju.

"When people sign a contract with travel agencies, we assume the responsibility for the whole tour. Once we find any of our clients go missing overseas, our first response is to search for them, followed by contacting the local police."

The 52,000-ton Italian cruise ship Costa Classica departed from Shanghai on Oct 15 for a four-day cruise to Jeju. It returned to Shanghai at 10 am on Monday as scheduled.

Bi Qun, of Costa Cruise, said this is the first time that Chinese tourists have gone missing in Jeju. "We have received no further information from South Korea. All we can do at this stage is to give the passengers' names to the local police and cooperate with them," she said.