London police are investigating the possibility that an executive working for Rupert Murdoch's News International deleted "millions of emails" in an attempt to thwart a phone hacking probe, reports said Friday.

On two separate occasions, a senior executive is thought to have erased "massive quantities" of messages, according to The Guardian.

One of the massive deletions may have happened in January, just as police were launching "Operation Weeting" to look into charges that reporters at News of the World hacked voicemails.

While Guardian didn't name the senior executive, current News International CEO Rebekah Brooks was editor of the British tabloid at the time.

News International chairman James Murdoch had pledged that the company was proactively cooperating with police.

"Currently, there are two major and ongoing police investigations," he said in a statement. "We are cooperating fully and actively with both. You know that it was News International who voluntarily brought evidence that led to opening Operation Weeting and Operation Elveden. This full cooperation will continue until the police’s work is done."

Forbes speculated that the new revelations would make News International's proposed takeover of Sky News even less likely.

Murdoch announced Thursday that News of the World would print its last edition Sunday, ending the paper's 168-year run.