Last Saturday, police in the central province of Nghe An said they had launched a criminal investigation and were hunting for a woman called Loan for "organizing or coercing other persons to flee abroad or to stay abroad illegally."

The probe was launched following a petition from Vu Thi Ly, one of the clients of the ring.

Ly, who resides in Nghe An's Yen Thanh District, said Loan helped with procedures for her to work in France.

Ly said she arrived in the European country as a tourist but was later expelled for using a fake visa.

The probe has gained some urgency after 39 people being trafficked to the U.K. were found dead in a refrigerated container truck last week. Fears have since surfaced and gained currency that most of the dead persons were Vietnamese, with several families in the central provinces of Ha Tinh and Nghe An reporting that their loved ones were missing, fearing the worst.

There has been no indication so far that Loan's operation was linked to the tragedy.

Also Saturday, police officers in Nghe An detained Le Duy Anh, 40, and three accomplices - Tran Thi Thanh, 60, Ho Thi Hang, 54, and 45-year-old Tran Thi Ha, and placed them under criminal investigation for "organizing or coercing other persons to flee abroad or to stay abroad illegally," a crime punishable by up to 20 years in jail under Vietnam's Penal Code.

Preliminary investigations showed that Anh was the director of an overseas study consulting center in Thanh Xuan District, Hanoi.

Anh colluded with his accomplices to find clients by promising to send them to Australia for better jobs.

They ran the operation illegally from September 2015 to January 2019. They received more than 400 applications and collected hundreds of thousands of U.S. dollars from customers.

However, none of the clients have been able to go overseas as promised.

Following the U.K. tragedy, Prime Minister Nguyen Xuan Phuc ordered relevant agencies to investigate cases of Vietnamese citizens taken illegally to foreign countries. Such violations must be strictly handled, he said.

Vietnam reported 490 human trafficking victims in 2018. The U.S.'s Trafficking in Persons Report 2019 said Vietnamese government has not fully met the minimum standards for the elimination of trafficking but is making significant efforts to do so.

Some 70 percent of Vietnamese trafficking cases in the United Kingdom between 2009 and 2016 were linked to labor exploitation, with young people forced to work in cannabis production and nail salons, according to a British government report last year.

A March report by the Pacific Links Foundation, a U.S.-based anti-trafficking organization, had identified Nghe An as home to many victims of human trafficking who end up in Europe.