Germany's federal cartel office Bundeskartellamt has continued its investigation against the country's two largest commercial TV broadcasters ProSiebenSat.1 and RTL.

At the beginning of February, officials raided RTL's offices again, the TV group confirmed to German news magazine "Focus".

The anti-trust authority's probe is based on the suspicion that RTL and ProSiebenSat.1 have jointly decided to encrypt their digital TV channels and make them only accessible to viewers if they pay an additional fee.

The cartel office commenced its proceedings in May 2010 . The latest raid was part of "further investigations", the competition watchdog told the magazine.