Dentsu Inc., Japan's largest advertising agency, said it may have lost three CD-ROMs containing personal information on about 54,000 shareholders.
The three disks containing data that included shareholders' names and addresses disappeared from Dentsu's Tokyo headquarters, it said in a statement Thursday to the Tokyo Stock Exchange. The disks did not include shareholders' telephone numbers and bank accounts, it said.
There "is a high possibility" the disks were disposed of by mistake and it was unlikely the information had been leaked outside the company or used improperly, Dentsu said in the statement.