Police in Okayama Prefecture, western Japan, have arrested a former temporary worker of a subsidiary of telecom firm NTT West in connection with a suspected leak of personal data.

NTT Business Solutions announced last year that a former temp worker leaked about 9.28 million cases of personal data, which was kept by 69 local governments and businesses. The worker was reportedly in charge of call center system operation maintenance.

Okayama prefectural police have been investigating the data leak case after they were contacted by Yamada Bee Farm, a health food company in the prefecture that potentially had about 4 million cases of data leaked.

On Wednesday, the police arrested 63-year-old Kageyama Masahiro in Ashiya City, Hyogo Prefecture, on suspicion of illegally taking customer information and leaking it to a list buyer in Tokyo.

The police suspect the worker downloaded file data containing customer information in January last year, copied it and sent it to the buyer.

The police say the suspect took information of about 32,700 customers of Yamada Bee Farm, including their names, addresses and telephone numbers. Such information was reportedly sold for a total of about 20,000 yen, or about 136 dollars.

Kageyama has reportedly admitted to the charges.

The Personal Information Protection Commission gave administrative guidance to two subsidiaries of NTT West last week for their failure to take appropriate measures regarding the case.

The governmental commission calls on the firms to improve steps to prevent such breaches.