Messages on murdered teenager Milly Dowler's mobile phone may have been "automatically" removed, a judge chairing an inquiry into press standards was told today.
A lawyer representing the Metropolitan Police told Lord Justice Leveson that it was "unlikely" that a private investigator employed by the News of the World altered the phone's voicemail settings.
Lord Justice Leveson said he would consider how to "get to the bottom" of what had happened.
Neil Garnham QC, representing the Metropolitan Police, told the inquiry that the date Mrs Dowler believed messages were deleted was before Glenn Mulcaire had been involved in the case for the newspaper.
Mr Garnham said: "The visit by the Dowlers to the Bird's Eye building occurred on March 24 2002.
"Secondly, Mr Mulcaire was not tasked in relation to the Dowler's until some time after that date.
"Third and accordingly, it is unlikely that anything Mulcaire did was responsible for what Mrs Dowler heard when she called Milly's phone during that visit. It's not yet possible to provide a comprehensive explanation for the fact that on that occasion the automatic 'mailbox full' message was not heard."
Mr Garnham went on: "It is conceivable that other News International journalists deleted the voicemails, but the Metropolitan Police Service have no evidence to support that."
He said the "most likely explanation" was that messages were automatically removed after 72 hours, and added that the network provider had confirmed that this was "a standard automatic function of that voicemail box system at the time".
There were approximately 72 hours between Milly's disappearance and when Mrs Dowler called the voicemail.
Mr Garnham said: "I can say from Metropolitan Police Service records that the Metropolitan Police did not tell the Dowlers that voicemails had been deleted, for the simple reason that they did not know of any such deletions."