Police officers are examining 3,870 names, along with 5,000 landline numbers and 4,000 cellphones, the government's Home Affairs Select Committee was told.
The Metropolitan Police’s deputy assistant commissioner Sue Akers, who is leading the probe, said that only 170 of the almost 4,000 potential victims have been contacted.
And speculation was growing that the true number of those hacked by the News of the World could run into the tens of thousands.
Ms Akers told MPs she was adopting a ‘very broad’ approach to the inquiry adding that victims of the phone hacking felt ‘violated’.
The investigation, called Operation Weeting, is expected to last for a number of years.
But Ms Akers said: “I hope that I do not have to come back here in five years’ time.”
The police investigation into wrong-doing by billionaire Rupert Murdoch's News of the World is expected to cost the British Tax payer millions of pounds.