The news came as Scotland Yard said a 63-year-old man was arrested in connection with allegations of corruption at an address in Surrey by officers investigating phone hacking.
Sources in Britain said the man is believed to be a private investigator who worked for the News of the World.
Ofcom, the British media regulator, said it would consult with police and MPs about the conduct of Mr Murdoch’s tabloids to determine whether his executives met the “fit and proper person” requirement for holding a broadcasting licence in Britain.
Two men were released on bail last night, having been arrested earlier yesterday.
Former Downing Street communications chief Andy Coulson, 43, and ex-royal editor of the News of the World Clive Goodman, 53, were quizzed at a separate police station over the phone-hacking scandal.
Both men were released on police bail until October.
Their arrests came as chief executive of News International Rebekah Brooks sought to reassure News of the World staff about what will happen next after the company decided to shut the paper.
She spoke to journalists yesterday, and pledged to find as many of them as possible jobs within the company in the wake of the closure.
A recording of part of her speech was leaked to Sky News, in which a disgruntled member of staff condemned her for calling the newspaper “toxic” and branded her “arrogant” to assume workers would want to stay at the media giant.
Ms Brooks issued a letter to all News International staff, saying she was not leading the company’s investigation into what has happened, and that no decisions had yet been made about a new publication.
British prime minister David Cameron also came under fire for an “appalling error of judgment” in appointing Mr Coulson as director of communications.
He said he took “full responsibility” for the appointment but insisted he had commissioned a firm to carry out a background check beforehand.
Labour leader Ed Miliband claimed Mr Cameron’s aides were handed a wealth of information warning them about practices Mr Coulson was involved in while editor of NOTW.
He said: “Putting it right for the prime minister means starting by admitting the appalling error of judgment he made in hiring Andy Coulson, apologising for bringing him into the centre of the Government machine, coming clean about what conversations he had with Andy Coulson, before and after his appointment, about phone hacking.”
The criticism came as Mr Cameron announced there will be an inquiry into the scandal.