Allegations that South Yorkshire Police officers 'falsified' witness evidence about the Hillsborough disaster are under investigation.
The Independent Police Complaints Commission has announced it is investigating a complaint from a group of Liverpool supporters which contains 'several allegations' about police officers falsifying evidence in the aftermath of the disaster.
Rachel Cerfontyne, deputy chair of the IPCC said: "We are pursuing several lines of enquiry related to this complaint, including alleged falsified reports of injuries sustained to a police horse near the Leppings Lane turnstiles.
"The complainants are being kept up to date."
The IPCC is currently investigating more than 160 complaints about police actions before, during and after the disaster, which involved the unlawful killing of 96 Liverpool supporters.
Offences being investigated by the IPCC include misconduct in a public office, perjury, perverting the course of justice and conspiracy to pervert the course of justice.
Ms Cerfontyne has also announced the IPCC's decision not to investigate a complaint against South Yorkshire Police chief constable David Crompton which claimed he had directed his legal team to blame Liverpool supporters at the recent inquests is to be reviewed.
She said she has commissioned 'an external independent review' of the decision after 'strong feelings' were expressed about the decision not to investigate Mr Crompton.
Ms Cerfontyne said: "As part of my decision, I concluded that any investigation would be 'significantly hampered' as it would be unable to access any communications between Mr Crompton and his legal team due to Legal Professional Privilege, and that the available evidence did not indicate that a criminal or misconduct offence had occurred.
"A number of options are being considered to provide an impartial and thorough scrutiny of the evidence that was assessed and which informed my final decision.
"I have instigated this process which will afford those involved, including the complainants, the right of review. It is essential that any reviewer is demonstrably independent of all parties, including the IPCC. I have always stated that I would be willing to revisit this decision should any new evidence come to light."
It has also been announced the IPCC has requested a copy of a new book about the Hillsborough disaster that is due to be published next month by former South Yorkshire Police chief inspector Norman Bettison.
Sir Norman, who denied during the recent inquests that he had been part of a ‘black propaganda unit’ to blame Liverpool supporters for the disaster, has said he has written the account - called 'Hillsborough Untold' - to combat ‘false accusations’.
Ms Cerfontyne said: "Its contents will be assessed in consultation with the CPS and together we will consider what impact, if any, it has on the criminal investigation and what action can be taken."
Both the IPCC and the parallel criminal investigation called Operation Resolve are due to submit full evidence files to the CPS by the turn of the year so decisions on whether to bring criminal charges can be made.
Operation Resolve is investigating a number of individuals and organisations to establish whether any had criminal culpability for their role in the Hillsborough disaster.
The scope of the investigation includes examining the full circumstances surrounding the planning and preparation for the match and events as they unfolded on the day of the disaster.
Operation Resolve is currently considering the following criminal offences as part of its investigation - gross negligence manslaughter, misconduct in public office, perverting the course of justice and potential breaches of the Safety at Sports Ground Act and Health and Safety at Work Act.