Tepco revealed that one of its employees has lost documents that include the personal information of 22 individuals who have applied for compensation related to the nuclear crisis, adding this was not the first such incident.

"We deeply apologize for causing trouble," a Tokyo Electric Power Co. official told reporters Friday, explaining that the employee, a man in his 40s, forgot the documents on a train while returning home Tuesday.

The utility has not received any reports of inappropriate use of the personal data.

Tepco further admitted there have been around 60 cases involving the mishandling of personal information linked to compensation claims, and that it decided to disclose the latest incident because it has not been able to contact all of the 22 individuals concerned.

They include evacuees from the town of Futaba, which cohosts Tepco's Fukushima No. 1 nuclear plant.

According to the utility's officials, the documents included the names and addresses of the individuals, as well as the details of their compensation claims.

The employee in question noticed Wednesday morning that he had left his bag containing the documents on the train. Tepco reported the incident to police, but the papers have not been found.