Updated

Britain's police watchdog said Thursday that it was investigating two senior police officers whose force failed to act on information that could have blown open the phone hacking scandal well before it erupted last year.

The Independent Police Complaints Commission said it was reviewing the conduct of Surrey Police's deputy chief constable, Craig Denholm, and the force's temporary detective superintendent, Maria Woodall.

Both allegedly knew that the now-defunct News of the World tabloid had hacked the cell phone of missing British schoolgirl Milly Dowler, whose disappearance in April of 2002 made national headlines. Dowler was eventually found dead, and the revelation — in July of last year — that the murdered teenager's privacy had been violated by journalists sent a wave of revulsion across Britain.

The outrage intensified as it became clear that Dowler was only one of hundreds of victims of tabloid intrusion. The scandal forced the closure of the News of the World, cost proprietor Rupert Murdoch his multibillion pound (dollar) bid for full control of satellite broadcaster BSkyB, and led to a series of overlapping police, parliamentary and regulatory inquiries on both sides of the Atlantic.

The scandal also focused attention on the cozy relationship between Murdoch's powerful media empire and some of the most senior police figures in the land. Three of Scotland Yard's most senior officers resigned in disgrace following the exposure of their professional, social, and personal ties to some of the main suspects in the scandal. Other officers — including a superintendent from the City of London Police, which covers the capital's financial district — have been arrested, although none have yet been charged.

Police in the southeastern England county of Surrey have also been dragged into the spotlight, particularly after it emerged that the force knew from the beginning that Milly's phone had been compromised. Surrey Police has yet to offer an explanation of why it didn't act on the information — although the revelation that the force had accepted money from Murdoch's News Corp. has raised questions about the nature of the force's relationship with the New York-based media company.

In a separate development, Scotland Yard said a 31-year-old former employee of Britain's National Health Service had been arrested by officers investigating corrupt links between public figures and News Corp. journalists. Scotland Yard said the man was suspected of corruption and conspiracy to cause misconduct in a public office. Police say the man was arrested at his home in west London early Thursday morning and is being questioned at a local police station.

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Associated Press writer Cassandra Vinograd contributed to this report.