The former editor of Britain's Daily Mirror tabloid was questioned by police on Friday over suspected phone hacking, media reported.
The development comes a day after four journalists from the Mirror Group, including another editor, were arrested on suspicion of illegally accessing voicemail messages.
London's Metropolitan Police said on Friday they had interviewed a 51-year-old man, named by media as former Mirror editor Richard Wallace.
"He was interviewed under caution -- not arrested -- in connection with the suspected conspiracy to intercept telephone voicemails at Mirror Group Newspapers," Scotland Yard said in a statement.
The man was questioned at a police station in south London and later released, it added.
James Scott, the editor of weekly tabloid The People, and his deputy Nick Buckley were arrested in dawn raids on their homes on Thursday, along with the Sunday Mirror tabloid's former editor Tina Weaver and her former deputy Mark Thomas.
The arrests represent a further widening of the hacking scandal which engulfed the rival British tabloid empire of Australian-born tycoon Rupert Murdoch in 2011.
Murdoch was forced to shut down his weekly News of the World in the wake of a storm of allegations that its staff illegally accessed the voicemail messages of a murdered schoolgirl and dozens of public figures.
The scandal sparked three police probes and a judicial inquiry that has called for a tough new watchdog to regulate Britain's famously raucous press.
Around 100 people have been arrested under various phone-hacking and corruption investigations sparked by the scandal at the News of the World.
Several people have been charged including Prime Minister David Cameron's former media chief Andy Coulson and Rebekah Brooks, former chief executive of Murdoch's British newspaper wing News International.
Lawmakers are due to vote on Cameron's proposals for a new press regulator on Monday.