It follows allegations that anonymous alterations to the Wikipedia page about the tragedy were made from computers on Whitehall's secure intranet.
A Merseyside newspaper said revisions to the online encyclopaedia began five years ago on the 20th anniversary of the tragedy, and again in 2012.
Among the reported amendments to the Hillsborough section was an insertion saying "Blame Liverpool fans", and two years ago the phrase "You'll never walk alone" was altered to "You'll never walk again."
A Cabinet Office spokeswoman said: "This is a matter that we will treat with the utmost seriousness and are making urgent inquiries.
"No-one should be in any doubt of the Government's position regarding the Hillsborough disaster and its support for the families of the 96 victims and all those affected by the tragedy."
Margaret Aspinall, from the Hillsborough Family Support Group, told a newspaper in Liverpool revelations had been deeply upsetting. She said: "I don't even know how to react, it's just so sad. I hear something like that and it upsets me a great deal, it makes me incredibly sad. I'm glad somebody has found out about it but I'm frightened to be honest that we haven't known until now."
Reports claimed the entries were made from IP addresses used by computers in government departments, including the Department for Culture, Media and Sport, the Treasury and the Office of the Solicitor General.
Further changes included altering the description of a statue of Liverpool's renowned former manager Bill Shankly on the Anfield Wikipedia page from "He made the people happy" to "He made a wonderful lemon drizzle cake".
A government computer was also reportedly used to change the phrase "This is Anfield", which is in the players' tunnel at the club's stadium to an offensive statement.