Scotland Yard detectives have arrested four current or former Mirror Group Newspaper journalists on suspicion of being involved in a phone voicemail hacking conspiracy involving the Sunday Mirror.

The three men and one woman were arrested early Thursday morning in separate raids in London, U.K. and are being interviewed at various police stations across the city.

Detectives are calling the alleged conspiracy a “separate” incident to the phone-hacking scandal that plagued Rupert Murdoch's now defunct News of the World.

“It is believed it mainly concerned the Sunday Mirror newspaper and at this stage the primary focus is on the years 2003 and 2004,” Metropolitan Police said in a news release.

Scotland Yard has not released the names of the suspects. They are described as a 40-year-old man from south-east London, a 47-year-old woman from south-west London, a 49-year-old man from south-west London, and a 46-year-old man from south-west London.

British newspapers are reporting that one of the suspects is current Sunday People editor James Scott.

Scott’s deputy editor Nick Buckley was also arrested.

In a statement published in the Guardian, a Trinity Mirror spokesperson, who represents the Sunday Mirror, said “We can confirm that James Scott the editor of the People and his deputy, Nick Buckley, were arrested this morning…. We understand that two former employees were also arrested this morning.”

According to the Guardian, the other two suspects arrested Thursday are Tina Weaver, the former-Sunday Mirror editor and Mark Thomas, the former People editor.

The arrests were a part of “Operation Weeting” – an investigation into phone hacking which began in 2011.

Last March, former News International executive Rebekah Brooks and her racehorse trainer husband Charlie were arrested along with four other suspects in connection to a scandal that began in 2005 when tabloid reporters allegedly broke into the voicemail systems of aides to the royal family.

Mirror Group Newspapers, a subsidiary of the Trinity Mirror Group, publishes the Daily Mirror and two Sunday tabloids, The People and the Sunday Mirror.

With files from The Associated Press