Kansai Electric Power Co. admitted Thursday it has not paid 12,900 employees a total of ¥1.7 billion in overtime wages for a two-year period through the end of last year.

The Osaka-based utility discovered the underpayments for late-night overtime work while investigating the suicide last April of an employee suspected of overwork. The investigations were mandated by labor authorities following the suicide.

Kansai Electric tallied the work hours of its 22,400 employees and will retrospectively make up the unpaid overtime wages, it said, adding that in five exceptional cases the firm owed each of the workers ¥3 million or more.

The company will compile a report on overtime labor based on the probe and submit its findings to labor inspection offices, it said.

The Tsuruga Labor Standard Inspection Office summoned the utility’s President Shigeki Iwane on Jan. 6 to provide information following the suicide of the employee.

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The labor office instructed the utility to analyze the working hours of all employees in managerial positions, since the employee who committed suicide officially held a management post.

The employee, a section chief in his 40s, worked more than 100 hours — sometimes up to 200 hours — of overtime per month prior to his suicide. He was apparently under pressure to complete a process that would enable Kansai Electric to seek regulatory approval to extend the operating life of two of its aging nuclear reactors at the Takahama plant in Fukui Prefecture.

The man committed suicide at a hotel in Tokyo in mid-April during a business trip and the Tsuruga labor office in Fukui concluded in October that overwork played a role in his death.

Under the Labor Standards Law, people in supervisory or management positions are exempt from restrictions on working hours and do not receive overtime pay. This provision unintentionally encourages lax management of work hours for people in such positions, experts say.

On Jan. 17, the utility said it received a “recommendation of correction” dated Dec. 20 from another labor inspection office in Osaka regarding unpaid overtime wages that were discovered through email records. Six employees were found to have been underpaid in that instance.

The company in January established a committee headed by the president to tackle the issue and announced new measures, including banning overtime exceeding 80 hours per month.

“We take the probe results seriously and realize a work environment where employees can perform well in good conditions,” the company said in a statement.

The incident came to light while the government is making efforts to rein in excessive work hours.

Prime Minister Shinzo Abe’s government is stepping up efforts to curb excessive work after labor authorities determined in September that a 24-year-old female employee at advertising giant Dentsu Inc. committed suicide in December 2015 as a result of karoshi, which literally means death from overwork.

The news of her suicide caused an uproar over endemic overwork at leading Japanese companies.

On Tuesday a government labor reform panel adopted a report setting the overtime limit at 45 hours per month and 360 hours per year. However, during busy periods, employees can work up to 100 hours of overtime in a single month, and up to 80 hours each month for a duration of two to six months.

The report, which has been endorsed by business lobby Keidanren and Rengo, otherwise known as the Japanese Trade Union Confederation, has been blasted by families of Karoshi victims, saying its call for creating the 100-hour overtime cap could effectively legalize long working hours at the expense of workers’ health.