The Hillsborough Independent Panel has released previously unpublished papers from around 80 organisations including the Government, police, emergency services, Sheffield City Council and the South Yorkshire coroner.
The families of the 96 football fans who died in Britain's deadliest sporting disaster were given access to more than 400,000 pages from 8am.
A report explaining the contents of the documents will be published by the panel, chaired by the Bishop of Liverpool, the Rt Rev James Jones.
Ninety-six Liverpool fans died in a crush at Sheffield Wednesday's Hillsborough stadium on April 15 1989 where their team were to meet Nottingham Forest in an FA Cup semi-final.
Liverpool's executive mayor, Joe Anderson, said: "With the release of these documents, we are hoping to get the truth of what happened.
A 1990 report into the disaster, by Lord Justice Taylor, found that the main reason for the disaster was a failure of "police control" but the Crown Prosecution Service decided there was insufficient evidence to bring a prosecution.
The victims' families say it is an injustice that no individual or organisation has been held fully accountable for the disaster. They believe a major incident plan was never initiated by South Yorkshire Police and fans in the Leppings Lane end were denied emergency medical attention.
The families also dispute the findings of an inquest into the deaths, which ruled that the victims were all dead, or brain dead, by 3.15pm and which subsequently recorded a verdict of accidental death.
Margaret Aspinall, chairwoman of the Hillsborough Families' Support Group, said they hope the documents will answer some of the questions they have about the causes and aftermath of the tragedy.
"This is what the families and the fans have been fighting for 23 years. Without the truth you cannot grieve and where there is deceit, you get no justice," Mrs Aspinall, 65, said.
People in Liverpool will observe a two minute silence today as a mark of respect for the victims.
It is expected the families will meet in the coming days to decide what action to take, if any, following the disclosures.