Former Daily Mirror editor Richard Wallace has been interviewed under caution by detectives investigating phone hacking at Mirror Group Newspapers.

The Metropolitan police confirmed on Friday that a 51-year-old man had been questioned as part of the Operation Weeting investigation into an alleged phone hacking conspiracy at the newspaper group.

Wallace attended a south London police station at approximately 1pm and was later released.

He was deputy editor of the Sunday Mirror between 2003 and 2004, before becoming editor of the Daily Mirror until 2012.

Wallace now works as a PR advisor to Simon Cowell in the US. He is believed to be flying back to the US on Saturday.

The police interview comes a day after Scotland Yard arrested four past senior Mirror Group editorial staff, including ex-Sunday Mirror editor Tina Weaver and current Sunday People editor James Scott, over what it suspected was a "separate conspiracy" to the News of the World phone-hacking, mainly involving the Sunday Mirror between 2003 and 2004.

Scotland Yard said in a statement: "A 51-year-old man attended a South London police station at approximately 1300 hours today. He was interviewed under caution (not arrested) in connection with the suspected conspiracy to intercept telephone voicemails at Mirror Group Newspapers, which is being investigated by Operation Weeting, and later released."

• To contact the MediaGuardian news desk email media@theguardian.com or phone 020 3353 3857. For all other inquiries please call the main Guardian switchboard on 020 3353 2000. If you are writing a comment for publication, please mark clearly "for publication".

• To get the latest media news to your desktop or mobile, follow MediaGuardian on Twitter and Facebook.