Police may have covered up their mistakes in stadium riot that killed 96 people in 1989.

A former top policeman called for a criminal investigation into the 1989 Hillsborough stadium disaster, a day after a report found police tried to cover up their errors by blaming fans for the tragedy.

Richard Wells, who was in charge of South Yorkshire Police from 1990 to 1998, said on Thursday it was "absolutely essential" that a criminal probe be held into the way police had handled the disaster in which 96 Liverpool fans died.

The force itself meanwhile announced it was reopening an investigation into its own conduct.

Members of the crowd react during a vigil at St George's Hall in Liverpool, northern England on Wednesday. British Prime Minister David Cameron said on Wednesday he was "profoundly sorry" for failures and cover-ups in the wake of the 1989 Hillsborough soccer disaster, in which 96 spectators died after a crowd crush in the stadium. Nigel Roddis / Reuters

And West Yorkshire's police authority said it would investigate the role played by current chief constable Norman Bettison, who at the time of the disaster was a serving officer in the South Yorkshire force.

Campaigners have called for Bettison, who insists the behavior of some fans inside Hillsborough made the police's job "harder than it needed to be", to resign.

As the ramifications of Wednesday's damning independent report into the disaster became clear, Football Association (FA) chairman David Bernstein offered "a full and unreserved apology" to all those affected.

Bernstein's statement only came after relatives had demanded the FA apologize for awarding the match to Hillsborough in Sheffield, south Yorkshire, even though the stadium did not have a valid safety certificate at the time.

After the report was published, the FA had initially issued a statement welcoming the findings but offering no apology over the events at the match between Liverpool and Nottingham Forest 23 years ago.

In the later statement, Bernstein went further.

"We are deeply sorry this tragedy occurred at a venue the FA selected," he said.

"This fixture was played in the FA's own competition, and on behalf of the Football Association I offer a full and unreserved apology and express sincere condolences to all of the families of those who lost their lives and to everyone connected to the city of Liverpool and Liverpool Football Club."

The report found that senior police officers had mounted a concerted campaign to cover up failings in the worst disaster in British football history.

In the most heart-rending of the findings, the independent panel found that 41 of the 96 who died might have survived if the emergency services' response had been better coordinated.

Many of the victims died from suffocation as they were crushed in the midst of a trapped crowd of fans.

On Wednesday, Prime Minister David Cameron apologized to the families of the dead and injured following the publication of the report, saying they had suffered a "double injustice".

Cameron said Attorney General Dominic Grieve would review the findings as soon as possible and decide whether to apply to the High Court for new inquests into the deaths to be held - a key demand of relatives of the victims.

The original inquests in 1990 and 1991 recorded verdicts of accidental death.

Relatives of the victims of the disaster have vowed to push for those responsible to face justice.

Liverpool's manager at the time of the disaster, Kenny Dalglish, who attended a vigil in the city on Wednesday, said on Twitter: "Very positive outcome. 23 years waiting for the truth next step justice."

Jack Straw, a former Labour Party interior minister, claimed that the police's reaction to the disaster had illustrated the "culture of impunity" created by the then Conservative government of Margaret Thatcher.

In comments that angered Conservatives, he said the police in the mid-1980s "really were immune from outside influences and they thought they could rule the roost, and that is what we absolutely saw in South Yorkshire".

Agencies