A British police investigation into illegal phone hacking by journalists has expanded beyond Rupert Murdoch’s disgraced News of the World tabloid to many other newspapers, the British Information Commissioner’s Office told CNN Thursday.

The Metropolitan Police asked the data-protection agency to hand over files from a 2006 investigation into the work of a private investigator who sold illegally obtained information to a wide range of newspapers, including the Daily Mail, Daily Mirror and News of the World.

The scandal over phone-hacking by News of the World forced the paper to close, prompted two top police officers to resign, and has put pressure on Prime Minister David Cameron, who hired a former editor of the paper to be his spokesman.

Police added 15 more officers to the investigation, boosting the existing team to 60, the officer in charge of the case said Thursday.

The increase comes in response to “a surge of enquiries and requests for assistance from the public and solicitors,” Deputy Assistant Commissioner Sue Akers said.

Police were already plowing through 11,000 pages of documents seized from a private investigator before they requested the additional files from the Information Commissioner.

The request for files from the Information Commissioner investigation came three months ago, the commissioner’s office said Thursday.

(Source: CNN)