The Ministry of Public Security announced Monday that criminal investigations have been launched against four men and one woman for "organizing and/or coercing other persons to flee abroad."

The crime is punishable by up to 20 years in jail under Vietnam’s Penal Code.

Three men – Tran Van Danh, 30, Nguyen Xuan Hung, 41, and Vu Nhat Tuan, 49, and a woman, Nguyen Thi Thanh Ha, 35, will be held in custody pending the investigation.

Vu Nhat Tuan (L) and Tran Van Danh

Nguyen Lam Sy, 35, was placed under house arrest.

Last March, four people, two Taiwanese and two Vietnamese, were prosecuted for forging travel documents, breaching the Employment Service Act and violating the Human Trafficking Prevention Law in the infamous case.

According to National Immigration Agency data, 56 of the 152 missing Vietnamese tourists were still at large in Taiwan as of February 19. Some of the people who surrendered or were found by police have admitted that they hoped to work in Taiwan illegally.

The missing tourists applied for electronic visas under the Kuan Hung visa program launched in 2015, which requires no visa fees for travelers from Indonesia, Vietnam, Myanmar, Cambodia, Laos and India. The program was part of Taiwan’s New Southbound Policy to establish closer ties with selected nations.

It also allowed simplified visa procedures for groups of five tourists or more from the six countries, as long as the tours were organized by "qualified travel agencies" recognized by the Taiwan Tourism Bureau or if they are part of company-sponsored groups.

Official statistics from Taiwan Tourism Bureau showed that a total of 225,702 foreign tourists touched down in Taiwan under the visa program since 2015.

Of these, 566 people have gone missing to work illegally in the territory, with Vietnamese accounting for 72 percent of the total.