Metropolitan Police had said they had found 91 PIN numbers -- used to listen in on a mobile phone's voicemail -- in the possession of jailed private investigator Glenn Mulcaire.
But at a hearing Friday, Jason Beer, the force's lawyer, said, "It is wrong to say that 91 is the answer, that that is the maximum. It may be on a bigger scale."
The hearing was called to organize and schedule the mushrooming lawsuits against Rupert Murdoch's News International, which owns the tabloid, The Guardian reported.
News International lawyer Michael Silverleaf said the company had offered to pay actress Sienna Miller $163,200 for the repeated hacking of her phone. The court also heard that Miller's former partner, actor Jude Law, was planning his own litigation, although his spokeswoman would not comment.
Detectives are still examining 9,200 pages of notes, mainly handwritten, from Mulcaire, who was convicted of intercepting voicemail messages in 2007, along with News of the World reporter Clive Goodman.
Beer said that since News International admitted liability in eight cases last week, police have been "flooded" with inquiries from possible victims.