Police have identified 829 "likely" victims of phone hacking and up to 6,000 more who might also have been targeted, the Leveson inquiry into media ethics was told today.
More than 4,000 phone numbers have been found in the notebooks of private investigator Glenn Mulcaire, Deputy Assistant Commissioner of the Metropolitan Police Sue Akers said.
She added that the investigation into alleged phone hacking - one of three major probes into alleged illegal activity - is approaching the "finishing line".
Operation Weeting began last January after Scotland Yard received "significant" information from News International - publishers of the now-axed News of the World - relating to the interception of voicemails.
The deputy assistant commissioner said 6,349 potential victims of phone hacking have been identified by name, and that of the 829 "likely" victims 581 have been contacted, 231 could not be contacted and 17 have not been contacted for "operational reasons".
Akers said there are 90 people working on the operation, including 35 tasked with working with the victims.
A total of 300 million emails that were originally thought to be lost have now been recovered and are being examined, Akers said.
Akers, who is overseeing all three probes, indicated that Operation Weeting was coming to a close.
She said: "We have a number of key witnesses that we will want to see and that process is ongoing now. It will take a few more months."
Questioning her, Robert Jay QC asked her: "You're probably nearer to the finishing line than the starting gun, is that right?"
She answered: "I'd like to think so, yes."
A total of 17 people have been arrested so far as part of Operation Weeting. No further action is being taken against two, with the remaining 15 currently on bail.
Akers is also overseeing Operation Elveden, looking into allegations that NI journalists made "inappropriate" payments to police.
She revealed the number of Scotland Yard officers assigned to the operation is set to increase.
"We have 40 police officers and staff but we are going to grow the team to take account of the fact that we moved last weekend into an investigation into The Sun, or journalists within The Sun."
There will eventually be 61 officers working on the operation, she said.
Asked about the progress made so far, Akers replied: "I am less confident in saying that we are near the end than the beginning of Elveden than I was when I made that comment about Weeting."
The third operation, Operation Tuleta, has been set up to investigate computer hacking. Akers said it is currently at the "scoping" stage and that the force is looking into launching a full investigation.
The Met has faced heavy criticism over the phone-hacking saga which intensified after it failed to reopen inquiries in 2009 amid allegations that thousands of mobiles were intercepted by journalists at the former Sunday tabloid.
Two of its most senior officers sensationally resigned over the scandal.
Then commissioner Sir Paul Stephenson made his shock announcement after coming under fire for hiring former News of the World deputy editor Neil Wallis and accepting free accommodation at a luxury health spa worth thousands of pounds. Assistant commissioner John Yates handed in his notice the next day following a furore over his handling of a review of the initial hacking probe.
A series of high-profile figures have been arrested in connection with police investigations, including former News International chief executive Rebekah Brooks and ex-Downing Street communications chief Andy Coulson.
Also appearing in front of the inquiry on Monday, former showbiz editor at the News of the World Dan Wootton said when he joined the newspaper in February 2007, it was made "absolutely clear" that illegal activity would not be tolerated.
"When I joined, obviously it was after Clive Goodman and Glenn Mulcaire had gone to jail, but myself and the rest of the staff were assured that that was an individual case," he told the inquiry.
"I guess the main thing that was most important to me was that when I started it was made absolutely clear that that sort of behaviour would not be tolerated in any way under (then editor) Colin Myler."
Sunday Mirror journalist Nick Owens also faced the inquiry on Monday, and denied going on a "fishing expedition" for stories about celebrities undergoing cosmetic surgery.
Owens had a meeting with Chris Atkins, the director of documentary Starsuckers, in which he was told of a fictional contact at a clinic who could provide details about confidential medical information.
The 2009 film planted invented celebrity stories in tabloid papers, Atkins has previously told the inquiry.
Owens was told he could have access to information on cosmetic work undergone by high-profile celebrities, and discussed payment and a confidentiality agreement with Atkins, the inquiry was told.
David Barr, counsel to the inquiry, asked Owens: "Doesn't this amount to a fishing expedition?"
The tabloid reporter replied: "I wouldn't say it was a fishing expedition. It was just a meeting in this very informal environment between two people to see whether there would be anything at the end of it that we would want to get involved in publishing."