Major lingerie and underwear maker Wacoal Holdings Corp. has launched surveys at outsourcing plants within Japan to make sure foreign trainees there are not subjected to unlawful labor practices, company officials said Monday.

The rare probe was launched earlier this year into conditions at 40 domestic plants for some 540 trainees who came from Vietnam, China and elsewhere under the government-sponsored technical training program. The factories include those not financially affiliated with the Wacoal group.

The Kyoto-based company found some problems at several plants and took steps to remedy them, they said.

The maker decided to investigate the labor conditions of trainees after a human rights group reported malpractice at a Myanmar outsourcing plant of a Wacoal unit in 2016.

"In addition to managing risks, we want to show to consumers that our manufacturing process is 'clean,'" said a Wacoal public relations official.

The 25 points surveyed include whether the trainees are paid at least the minimum wage and if they have returned to their home countries or gone missing before the end of their terms.

The company also requests some 30 documents, such as payroll books and training plans for the foreign trainees.

In June, the Ministry of Economy, Trade and Industry urged the Japanese textile industry to observe laws and regulations after discovering a series of violations in which foreign trainees were paid below the minimum wage or unpaid for overwork.

Japan introduced the training program in 1993, with the stated aim of transferring skills to developing countries. But the system has faced criticism at home and abroad as a cover for importing cheap labor.