Hillsborough disaster witness statements given to police by fans could have been doctored, it has emerged.
The evidence has been uncovered by the Independent Police Complaints Commission.
The watchdog said some fans’ accounts –used in the West Midlands Police investigation into South Yorkshire Police’s conduct – could have been altered.
The IPCC said 90 police notebooks which could contain crucial new information about the 1989 disaster at Sheffield Wednesday’s football ground have also been recovered.
The IPCC, which revealed last month it was looking for the notebooks, said 90 had been handed to South Yorkshire Police by retired and serving officers.
The force has also found boxes of notebooks and other documents covering the period of the disaster, which could contain vital details.
The IPCC also said it has uncovered evidence to suggest the statements of 74 more officers might have been changed – in addition to the 164 already identified by the Hillsborough Independent Panel – and 55 found by the IPCC earlier in its investigation.
Deborah Glass, IPCC deputy chairman, said: “This is an ongoing criminal investigation the like of which has never been seen before in this country. Already we are uncovering more about the disaster and its aftermath.
“Hillsborough has had a history of inquiries by the police and others, many completed quickly, coming to flawed conclusions.
“Our investigations need to deliver the last, definitive account.”
The disaster, that claimed the lives of 96 Liverpool Football Club supporters, is now at the centre of the biggest ever inquiry into police conduct in the UK.
Next week, the IPCC is planning to appeal for witnesses to contact them as they investigate the West Midlands Police inquiry into South Yorkshire Police’s handling of the disaster.
Ms Glass said: “This appeal forms a crucial element to our investigation into how West Midlands Police conducted its inquiries.”