GENEVA (AP) -- Switzerland's leading telecommunications company says prosecutors are starting a criminal investigation into who illegally provided four internal files to a top Swiss newspaper.
Swisscom says the Neue Zuercher Zeitung was given backup files from 2008 to 2010 that contained internal data including employee emails. It says the newspaper has returned three of the files.
The newspaper says it received the leaked files somewhat mysteriously a few months ago and used them for a story Wednesday in which it said the files include company and customer information including 600,000 phone numbers.
The company says prosecutors filed criminal charges "against persons unknown," since the breach appears to be "motivated by criminal intent." Switzerland allows prosecutors to file charges against unnamed people while they investigate.
Prosecutors were not immediately available for comment.