About ¥18 million has been stolen from bank accounts linked to NTT Docomo Inc.'s e-money service, the company said Thursday, prompting police to begin an investigation into a suspected scam.

As of Thursday, 66 cases of improper withdrawals from bank accounts linked to the mobile carrier's e-money service had been confirmed, NTT Docomo Vice President Seiji Maruyama told a news conference in Tokyo.

"We apologize to the victims" of the improper withdrawals, Maruyama said at the news conference, which was also attended by other company executives.