It may not be possible to identify who used government computers to post "sickening" comments about the Hillsborough disaster, the Cabinet Office has warned.
Officials said the passage of time and number of people using the Whitehall intranet made finding those who edited Wikipedia "challenging".
Relatives' groups and Liverpool-born MP Andy Burnham, a long-term campaigner on the issue, are being drafted in to monitor the investigation, a spokeswoman said. The Liverpool Echo reported revisions to the Wikipedia began five years ago on the 20th anniversary of the tragedy, and again in 2012.
The Cabinet Office spokeswoman said: "The amendments made to Wikipedia are sickening. The behaviour is in complete contravention of the Civil Service Code. It is entirely unacceptable."
Families of those who died at Hillsborough have reacted angrily to claims that offensive remarks about the disaster were posted from government offices.
A report by the Liverpool Echo alleges computers on the secure Whitehall intranet were used to add the phrases 'Blame liverpool fans' and 'you'll never walk again' to the Hillsborough Wikipedia page.
The Cabinet Office is launching an urgent inquiry into the matter:-
VIDEO: SHEILA COLEMAN, HILLSBOROUGH JUSTICE CAMPAIGN
The first of two IP addresses used in making offensive edits to the Hillsborough disaster page on Wikipedia, 188.8.131.52, can be traced to gateway-101.energis.gsi.gov.uk.
The second of the two IP addresses used to make offensive changes to the page, 184.108.40.206, can be traced to gateway-202.energis.gsi.gov.uk.
The edits to the Hillsborough disaster page on Wikipedia were made by IP addresses 220.127.116.11 and 18.104.22.168, both of which belong to government networks.
Twenty-two people have now been identified as suspects by two ongoing investigations into the Hillsborough disaster, including some who were not police officers.
Yesterday, the Independent Police Complaints Commission (IPCC) confirmed 13 retired or serving police officers were now being regarded as suspects as part of its inquiry into the aftermath of the 1989 tragedy in Sheffield.
Today, the IPCC said Operation Resolve - the wider criminal investigation into the disaster - has also identified 13 people "who fall within the suspect category".
It said six of these are retired police officers and seven worked for other, non-police organisations.
As the commission said four of those identified are being treated as suspects by both investigations, the total number of people being treated in this manner is now 22.
Thirteen retired or serving police officers have been identified as "suspects" in the ongoing investigation into the Hillsborough disaster, the Independent Police Complaints Commission (IPCC) has said.
The commission said 11 of these had already been interviewed under caution relating to a range of offences including manslaughter as well as misconduct in a public office and perverting the course of justice.
A spokesman said the other two would be interviewed in the near future.
The spokesman said four of the 13 have been identified as suspects as part of both the IPCC's investigation and also Operation Resolve - the criminal investigation into the 1989 tragedy.
The IPCC's inquiry - the biggest it has ever undertaken - covers the actions of the police in the aftermath of the crush at Hillsborough stadium, in Sheffield, which left 96 Liverpool fans dead.
The investigation was announced after the commission reviewed the report of the Hillsborough Independent Panel, which undercovered a huge amount of new evidence about what happened during and after the tragedy.
It is examining allegations including those surrounding amendments to police statements, the actions of the police officers after the disaster and the role of West Midlands Police, which investigated what happened at the time.
Operation Resolve, under the command of assistant commissioner Jon Stoddart, the retired chief constable of Durham Police, is a new, wider-ranging criminal investigation into the disaster.
The IPCC said it could not give any further information about the people who had been arrested and how many of them had been interviewed in relation to allegations of manslaughter.
Police officers involved in the Hillsborough disaster are being questioned as suspects for the first time.
Twelve retired police officers and one serving officer are being interviewed.
Elevenhave already been questioned under caution about a range of offences - including manslaughter, misconduct or perverting the course of justice.
In four days time, new inquests into the deaths are due to begin in Warrington. No one has ever been charged over the disaster.
ITV News Correspondent Damon Green reports:
Thirteen retired or serving police officers have been identified as "suspects" in the investigation into the Hillsborough disaster, the IPCC has said.
11 of these had already been interviewed under caution relating to the offences, which include manslaughter, misconduct in a public office, and perverting the course of justice.
A spokesman said the other two would be interviewed in the near future.
The police watchdog - The Independent Police Complaints Commission - say they have identified a total of 13 individuals - 12 former and one serving police officer - as suspects in their investigation into the Hillsborough disaster.
The suspected offences include manslaughter, perverting the course of justice, and misconduct in a public office. Four of those identified are also of interest to the criminal inquiry into the disaster, the IPCC said.
We've identified 12 retired police officers & 1 serving as suspects in our Hillsborough investigation. 4 are also of interest to Op Resolve
Hillsorough investigation: Suspected offences include perverting the course of justice, misconduct in a public office and manslaughter
Lawyers at the inquests into the deaths of 96 people in the Hillsborough disaster have expressed their "considerable regret" for a delay in providing pathology reports to the families of the deceased.
At a preliminary hearing today, counsel to the inquests Christina Lambert QC acknowledged that it was an "extremely difficult and tense time" for the families as the coroner, Lord Justice Goldring, was asked to delay part of the hearing, which are due to start on Monday.
Judy Khan QC, representing 74 families, asked the coroner for a three week break so the families could consider the late pathology reports.
Ms Khan asked for this to take place after the opening statements from the coroner and the families, which are due to start next week after a jury has been selected.
The coroner agreed to allow a delay but said he wanted lawyers at the inquest to liaise on how long this should be.
He agreed that this will take place after his opening statement and after the background "pen portraits" of all the victims which are to be presented by the families after the coroner has finished his opening.
These are scheduled to be completed by April 29.
Ms Lambert said: "It is matter of considerable regret that we were not able to provide the families with the pathology reports earlier.
"We recognise fully this has placed an emotional burden on families at an extremely difficult and tense time for them."