A photograph has emerged apparently showing Ian Tomlinson with a head injury before his death during the G20 protests.
The police watchdog said it was examining CCTV and pictures but refused to be drawn on the latest image, which was shown on Sky News.
Asked if it would form part of an investigation, an Independent Police Complaints Commission (IPCC) spokesman said: "We're looking at lots of CCTV and images from various places, but we're not going to give a running commentary on an ongoing criminal investigation."
A solicitor representing the officer caught on camera apparently pushing Mr Tomlinson requested a third post-mortem examination, which was carried out on Wednesday by a City of London coroner. The results have not yet been released.
The first examination, conducted by Dr Freddy Patel, found Mr Tomlinson died from a heart attack after he collapsed during the protests in the City on April 1.
But the second, carried out at the request of Mr Tomlinson's family and the IPCC, rejected that finding.
The second pathologist, Dr Nat Carey, found the 47-year-old died from internal bleeding.
His conclusions prompted IPCC investigators to question the officer, a constable in the Metropolitan Police Territorial Support Group (TSG) based in Lambeth, on suspicion of manslaughter.
