London ? Scotland Yard’s assistant commissioner resigned Monday, a day after his boss also quit, and fresh investigations of possible police wrongdoing were launched in the phone hacking scandal that has spread from Rupert Murdoch’s media empire to the British prime minister’s office.

Prime Minister David Cameron called an emergency session of Parliament on the scandal and cut short his visit to Africa to try to contain the widening crisis. Lawmakers today are to question Murdoch, his son James and Rebekah Brooks, the former chief executive of Murdoch’s U.K. newspaper arm.

In a further twist, a former News of the World reporter Sean Hoare, who helped blow the whistle on the scandal, was found dead Monday in his home, but it was not believed to be suspicious.

Murdoch shut down the News of the World tabloid after it was accused of hacking into the voice mail of celebrities, politicians, other journalists and even murder victims.

The crisis has roiled the upper ranks of Britain’s police, with Monday’s resignation of Assistant Commissioner John Yates — Scotland Yard’s top anti-terrorist officer — following that on Sunday of police chief Paul Stephenson over their links to Neil Wallis, an arrested former executive from Murdoch’s shuttered News of the World tabloid whom police had employed as a media consultant.

The government quickly announced an inquiry into police-media relations and possible corruption.

Home Secretary Theresa May said people were naturally asking “who polices the police,” and announced an inquiry into “instances of undue influence, inappropriate contractual arrangements and other abuses of power in police relationships with the media and other parties.”

The Independent Police Complaints Commission also said it was looking into the claims, including one that Yates inappropriately helped get a job for Wallis’ daughter. Wallis, former executive editor of News of the World, was arrested on suspicion of conspiring to intercept communications.

Yates said he had done nothing wrong.

“I have acted with complete integrity,” he said. “My conscience is clear.”

In another development, police confirmed that a second former News of the World employee was employed by Scotland Yard. Alex Marunchak had been employed as a Ukrainian language interpreter with access to highly sensitive police information between 1980 and 2000, the Metropolitan Police said.

Scotland Yard said it recognized “that this may cause concern and that some professions may be incompatible with the role of an interpreter,” adding that the matter will be looked into.

The prime minister is under heavy pressure after the resignations of Stephenson and Yates, and Sunday’s arrest of Brooks — a friend and neighbor whom he has met at least six times since entering office 14 months ago — on suspicion of hacking into the cellphones of newsmakers and bribing police for information.

Cameron’s critics grew louder in London as he visited South Africa on a two-day visit to the continent already cut short by the crisis. He dropped stops in Rwanda and South Sudan as his government faces growing questions about its cozy relationship with Murdoch’s media empire during a scandal that has taken down top police and media figures with breathtaking speed.

Parliament was to break for the summer today after lawmakers grilled Murdoch, his son James and Brooks, in a highly anticipated public airing about the scandal. Cameron, however, said lawmakers should reconvene Wednesday “so I can make a further statement.”