A technology firm has told British legislators it was aware of the deletion of hundreds of thousands of emails at the request of News Corp unit News International between April 2010 and last month, parliamentarian Keith Vaz said on Monday.

The revelation came in a letter by the firm, HCL, to the Home Affairs Select Committee, of which Vaz is chairman.

I am most surprised by the contents of the letter sent on behalf of HCL, Vaz told Reuters. The fact that so many emails have been deleted at the request of News International raises a number of further questions which we will continue to probe.

British police are investigating the extent of phone-hacking at the now defunct News of the World Sunday tabloid which was owned by News International, the British newspaper arm of Rupert Murdoch's media empire.

The paper had long maintained that illegally hacking into the voicemails of celebrities and members of the royal family had been confined to one rogue reporter who was jailed for four months in 2007.

But police now have a list of 4,000 possible targets including a missing schoolgirl, later found murdered, and families of victims of the 2005 London bombings, as well as politicians and celebrities.

Last month, senior police officers appeared before Vaz's committee and said News International had tried to thwart an original inquiry into phone hacking at the paper five years ago.

HCL told the committee in its letter that it had been involved in nine separate episodes of email deletion but did not know of anything untoward behind the deletion requests.

HCL says it is not the company responsible for emails on the News International system that are older than a couple of weeks. It says another unnamed vendor is responsible, but confirms it has co-operated with this vendor in deleting material.

It said that since it was not the company that stored News International's data any suggestion or allegation that it has deleted material held on behalf of News International is without foundation.

News International said in a statement it had been actively working since January with the police on email data and other computer information which may be relevant to their inquiry.

NI keeps backups of its core systems and, in close co-operation with the (police's) Operation Weeting team, has been working to restore these backups, the company said.

(Additional reporting by Stefano Ambrogi; Editing by Jon Hemming)