The Health, Labor and Welfare Ministry plans to have inspectors make unannounced nighttime visits to companies to clamp down on unpaid overtime and prevent deaths from overwork, ministry sources said Monday.

Such inspections by the ministry's labor standards inspection offices are typically conducted during the day. But the ministry has concluded that nighttime checks are necessary to push firms to stop the practice, the sources said.

Before making a surprise visit, inspectors will draw up a detailed inspection plan after receiving complaints, and inspectors will share information from the department handling claims for labor accident compensation as well as subsequent research on working hours, overtime pay and health checks on employees related to the claims.

If a claim is filed for compensation for a death due to overwork, the offices may also issue instructions to the company concerned to improve work conditions even before the claim is approved, as other employees in the same workplace may be subject to similar conditions, the sources said.

In December 2001, the ministry eased the standard for worker compensation claims regarding death from overwork and expanded compensation to include extended periods of overwork.

In February 2002, the ministry issued a guideline asking companies to send employees with an average 80 hours or more of overtime a month for medical checkups by industrial physicians.

The number of deaths and illnesses linked to overwork has been increasing. The number officially recognized in fiscal 2002 was 317, more than double the figure for the previous 12-month period and the highest since the government started compiling data in fiscal 1987.