The BBC understands those arrested include former assistant editor Jules Stenson, two former showbiz editors - Rav Singh and Polly Graham - and former features editor Matt Nixson.
BBC: Ex-News of the World staff bailed in phone-hacking probe
2.
In another development on Thursday, it emerged Sun features editor Matt Nixson had been sacked from the paper in relation to an investigation into the time he was at the News of the World.
BBC: James Murdoch evidence questioned by former executives