According to a statement published today by the Independent Police Complaints Commission, new evidence has emerged to suggest witness accounts relating to the Hillsborough disaster may have been altered.

On the eve of the one-year anniversary of the Hillsborough Independent Panel report's publication, Deborah Glass, IPCC deputy chair, released an update on the progress of investigations into the disaster.

The police watchdog believes accounts given by fans who attended the match on April 15, 1989, may have been changed.

The statement read: "From our work we have recovered West Midlands policy books that have never been seen by previous inquiries.

"We have identified the statements of 74 more officers which may have been amended. We have also uncovered material which would suggest that fans' witness accounts may have been altered.

"We have recovered pocket notebooks from officers who were on duty on the day of the match. We are in the process of interviewing all the surviving officers whose accounts were amended.

"We are also about to issue an appeal for witnesses. This appeal, which will be launched next week, forms a crucial element to our investigation into how West Midlands Police conducted its enquiries into the disaster.

"We want to hear people's experiences of that process. We have already had a number of people contact us with concerns that their statements were amended and we have no doubt there are others who have not contacted us: we want to be able to present as full as possible a picture of witness evidence both for the inquests and the criminal investigations.

"I cannot emphasise enough the significance of all this work. It builds on the work of the Hillsborough Independent Panel. But their work was a starting base. I acknowledge and understand the views of those who want quicker progress, and I cannot ask those who have waited 24 years to be patient.

"But I would ask them to speak to us to understand the complexity of the investigation we are conducting and the progress we are making; see for themselves the dedication and professionalism of our staff; and to continue to assist us in our work."