Executives of the Nippon Telegraph and Telephone group were asked Friday to investigate allegations that more than 10 of its employees released private data on NTT subscribers, officials of the Posts and Telecommunications Ministry said.

The request was made after the Asahi Shimbun reported on Friday that employees of the former NTT Corp. leaked customer information to brokers who sold it over the Internet.

NTT was reorganized Thursday into a holding company in charge of two regional companies, a long-distance and international service provider and NTT Mobile Communications Network Inc. (NTT DoCoMo).

The leaked information included the names, telephone numbers, addresses, birthdays and bank account numbers of NTT subscribers. Brokers of such information profit by charging fees to locate data on people based on their telephone numbers. One such order, usually made over the Internet, costs between 5,000 yen and 100,000 yen, the newspaper reported.

NTT-East and NTT DoCoMo jointly held a press conference the same day in Tokyo and said they have not yet confirmed the allegations made in the newspaper report.

However, the two companies said that if the report is true, it would be "truly regrettable." They pledged to do their utmost to stop employees from selling private customer information.

Specifically, the companies said they were developing computer software that analyzes access records to reveal suspicious database operations. The software is due for completion in September, the officials said.

For now, however, it is virtually impossible to catch employees if they retrieve the information little by little, they said.

There are about 80,000 NTT employees who have access to customer databases, and that makes investigations of data leak allegations very difficult, they said.