JEJU (Yonhap) ― A group of Vietnamese people who visited South Korea without a visa have disappeared from the country‘s resort island of Jeju, authorities said Friday.

The 46 are among 155 Vietnamese who came to the island on Tuesday for a six-day trip. Ten others who attempted to flee ― nine men and one woman ― were caught earlier this week and are under investigation, according to the local immigration office.

The immigration office said it is investigating if they were trying to look for illegal employment in South Korea.

“If they go outside the (Jeju) province, they will be charged with violating the Special Act on the Establishment of Jeju Special Self-Governing Province and the Development of a Free International City,” an official from the office said. “If they are caught over illegal employment, they will be charged with the violation of immigration control law.”

The Vietnamese tourists can leave the country on Sunday as planned if they are cleared of suspicion, the official added.

Police and the Coast Guard said they have stepped up inspections to prevent the missing Vietnamese from fleeing to other provinces.

Under the special act for Jeju island, all visitors except for nationals from terrorism-linked countries can enter and stay on the resort island without a visa for up to 30 days if the purpose of their stay is tourism.