Up to 1000 additional officers may be added to the 1444 members of South Yorkshire Police being investigated, the Independent Police Complaints Commission (IPCC) said.
The new figure was revealed as senior IPCC figures appeared before the Home Affairs Select Committee yesterday.
It includes officers from around 20 other forces who were present when 96 Liverpool fans died during an FA Cup semi-final in 1989.
The Committee was also told Sir Norman Bettison's resignation from West Yorkshire Police would not stop any investigation into his conduct after the tragedy.
Further inquiries into the disaster are being carried out by the IPCC and the Director of Public Prosecutions.
The investigations were prompted by the Independent Hillsborough Panel Report, which found police and emergency services had made "strenuous attempts" to deflect the blame for the disaster – in which 96 people died – on to fans.
It found that 164 police statements had been altered – 116 of them to remove or change negative comments about the policing of the fixture.
Earlier, Home Secretary Theresa May said she was talking to the IPCC about any extra resources needed to carry out the inquiry.
