Thousands of official documents relating to Britain's 1989 Hillsborough football disaster, in which 96 Liverpool fans died, were to be published for the first time Wednesday.
Relatives of the victims -- who died after a crush at Sheffield Wednesday's Hillsborough stadium in Yorkshire, northern England -- hope the papers will shed new light on what happened.
The documents come from the archives of 80 organisations including the British government, South Yorkshire Police, Sheffield City Council, the South Yorkshire coroner and the fire and ambulance services.
Government papers are not usually published in Britain until 30 years after they were written, but lawmakers agreed in August last year to the full, uncensored disclosure of all papers relating to the tragedy.
The decision came after more than 100,000 people signed an online government petition to trigger a parliamentary debate on the release of papers about the disaster, which happened during an FA Cup semi-final against Nottingham Forest.
The e-petition currently has more than 156,000 signatures.
The families of those who died in Britain's deadliest sporting disaster were to have the first access to more than 400,000 pages of documents in Liverpool on Wednesday morning, before the files are disclosed to the public in the afternoon.
The Hillsborough Independent Panel, which is overseeing the release, is publishing a report explaining the documents' contents.
David Cameron was due to make a statement about the report to lawmakers later.
A report by judiciary chief Peter Taylor, published in 1990, found that the main reason for the disaster was a failure of "police control".
Victims' families say it is an injustice that no individual or organisation has been held fully accountable for the disaster.
They claim local police failed to initiate emergency planning and that fans in the Leppings Lane end of the ground were denied immediate medical attention.
"We do want accountability for 96 lives," Margaret Aspinall, whose son James died in the disaster, told BBC television.
"It is going to be hopefully a good day for the city, for the fans, but most importantly for the families, and hopefully we get what we should have had 23 years ago," added Aspinall, the chairwoman of the Hillsborough Families Support Group.
The city of Liverpool will hold a two-minute silence at 15:06 local time (14:06 GMT) -- the time the match was called off -- as a mark of respect to the victims, ahead of a a candle-lit vigil.
"The importance of this day cannot be underestimated, as it will trigger the start of a process which will lead to justice for everyone affected by the tragedy," said Joe Anderson, the city's executive mayor.
"We know the city will want to stand shoulder to shoulder with those affected by Hillsborough and share their sadness together as a city and support each other through this emotional time," he added.