Three more Vietnamese men in a foreign trainee program in Japan were made to take part in radioactive decontamination work in Fukushima Prefecture, which was devastated by the March 2011 nuclear crisis, their supporters said Wednesday.

The Justice Ministry’s Immigration Bureau is conducting a probe, believing more foreigners may have been made to engage in inappropriate work under the Technical Intern Training Program.

Japan introduced the program in 1993 with the aim of transferring skills to developing countries. But the scheme, applicable to agriculture and manufacturing among other sectors, has drawn criticism at home and abroad for giving Japanese companies a cover to importing cheap labor.

According to the Zentouitsu Workers Union, which supports foreign trainees, the three Vietnamese men came to Japan in July 2015 and conducted radiation cleanup work in Fukushima Prefecture between 2016 and 2018 as trainees of a construction company in the city of Koriyama in the prefecture.

Their contracts only stated that they would be engaging in form-work installation and reinforcing steel placements, and the company did not give them a detailed explanation of the decontamination work beforehand.

In March, a Vietnamese trainee hired by a construction firm in Morioka, Iwate Prefecture, said at a news conference in Tokyo that he had been misled into conducting decontamination work in Fukushima Prefecture.

The Justice Ministry and the Ministry of Health, Labor and Welfare have released statements saying that decontamination work does not fit the purpose of the trainee program.