The family of a Brazilian man shot dead by police in London in 2005 has called for the News Corp phone-hacking investigation to be widened.
In a letter to UK PM David Cameron, Jean Charles de Menezes' relatives say the actions of police who investigated Mr Menezes' death should be probed.
They say officers may have leaked confidential information to the media.
The phone number of a cousin of Mr Menezes was seized from an investigator hired by The News of the World.
Twenty-seven-year-old Mr Menezes was mistakenly shot dead on an underground train at Stockwell station six years ago.
He was wrongly identified as a suicide bomber days after the 7 July bombings which rocked the capital.
The family of Mr Menezes was officially informed on Wednesday that the mobile number of one of his cousins, Alex Pereira, was found in documents that belonged to private investigator Glenn Mulcaire.
The police have now collected the details of other family members to check whether they had also been hacked.
A relative of Mr Menezes, Vivian Figueiredo, told the BBC that at some stages of the investigation it looked like private information on the case was being leaked to the media.
In the letter to Mr Cameron, the Menezes family says some members the London Metropolitan Police were too close to journalists from Rupert Murdorch's News Corp organisation.
A spokesperson for the Justice4Jean campaign group, Estelle du Boulay, said the Menezes family were shocked by the news that they may have been hacked at a time when they were most vulnerable and bereaved.
"They fear the police may be attempting to cover up their own wrongdoing once more relating to this case," said Ms Du Boulay.
The Menezes family has called on Mr Cameron to do everything within his power to ensure that the issue is thoroughly investigated.