In the latest twist to the phone-hacking case, Indian IT major HCL Technologies has said that it was asked to delete thousands of emails of Rupert Murdoch's News International (NI) on four more occasions than had been previously disclosed.

Responding to the latest disclosure by HCL, Keith Vaz, chairman of the Home Affairs Select Committee, said: "The request for deletion of folders and emails by News International is concerning".

"The Committee will continue to investigate the issue of phone hacking and the removal of any information that could possibly point to the prevalence of phone hacking by those working in the organisation," the Indian-origin lawmaker said.

In a letter to Vaz, the legal company acting on behalf of HCL outlined four separate occasions when News International requested deletion of folders and emails between December 2009 and June 2011.

These include emails from an inbox of a user who has not accessed his email account for eight years and the removal of a personal folder.

In its earlier communication to the committee probing the phone-hacking issue, HCL said on August 1 insisted that it did not store News International's emails and thus could not be responsible for their deletions, but went on to cite nine instances of email deletions between April 2010 and July 2011.

The latest revelations come after the company conducted further searches.

The letter to Vaz said: "You will recollect from my earlier letter my concern that the very short time frame given by you to HCL for its initial response did not permit a more comprehensive search".

The letter to Vaz further added: "During the course of these further searches by my client, which have been more extensive but still focused on the question raised by you of requests or instructions from News International concerning deletions, four further occasions have been identified".

Giving details of the four deletions, the letter said that on December 9, 2009, NI requested deletion of emails from the inbox of a user who had not accessed his email account for eight years.

The action was completed.

On February 24, 2010, NI requested the deletion of personal folders under the name "Gabriel/uploaded".

The action was completed.

On September 28, 2010, another request was made by NI to remove a personal folder.

The requested files were removed, and on 29 June 2011, NI requested the deletion of certain bad or corrupted files.

The requested files were deleted, the letter said.

A total of 16 people have now been arrested on suspicion of phone hacking since 'Operation Weeting' - Scotland Yard's fresh investigation into the illegal interception of voicemails - was launched in January.

Former News International chief executive Rebekah Brooks and ex-Downing Street communications chief Andy Coulson are among those who have already been arrested as part of the inquiry.

The scandal has led Metropolitan Police Commissioner Paul Stephenson and Assistant Commissioner John Yates to resign, and the News of the World to close down in July after 168-years of publication.

The tabloid's royal editor Clive Goodman and a private detective Glenn Mulcaire were jailed for hacking in 2007.

Police reopened the case in January this year after fresh allegations emerged that a murdered girl was among those targeted by journalists of the News of the World.