A recent probe into Japanese firms using the state-sponsored Technical Intern Training Program to deal with acute labor shortages has revealed 759 cases of suspected abuse, including unpaid wages, the Justice Ministry said Friday.

The findings confirm growing concerns about the link between the interns' working conditions and their disappearances from work. Last year, the number of missing foreign trainees rose to 9,052, compared with 7,089 the previous year. As of December, 328,360 foreign people were registered as technical interns.

The results of the probe showed that 231 interns weren't paid overtime wages and another 58 were being paid below the legal minimum. One intern was paid only ¥60,000 per month during a 7-month stint and received an hourly payment of ¥700 for an average of 60 hours of overtime per month.