Time Warner has lost data back-up tapes containing the personal employment and family details of 600,000 current and former employees.
The media group said a container of its computer back-up tapes was lost by an outside data storage firm in the US during shipment to one of that firm’s storage facilities.
Time Warner has used the firm to ship and store its computer back-up tapes offsite for several years, as part of its regular processes to protect its computerised data.
The missing tapes did not include personal data on Time Warner customers.
The US secret service is investigating the matter, working closely with Time Warner and the outside data storage firm.
“To date, the investigation has not found any evidence that the tapes or their contents have been accessed or misused,” said a spokesperson for Time Warner.
“Time Warner is today notifying individuals whose information may have been on the missing tapes of this incident and of resources at their disposal to monitor their credit reports in the event of unusual activity.”
This includes giving employees free credit checks with commercial credit agencies.