The March4Justice group delivered a petition to Downing Street
Five families who lost their loved ones in the Hillsborough disaster have handed in a 40,000-signature petition to 10 Downing Street.
Joined by more than 4,000 supporters, they marched through the streets of London to demand further investigation into the events of 15 April 1989.
Jenny Hicks, who lost her two daughters in the tragedy, said it was time that "someone took responsibility".
The petition was handed in just after 1430 BST on Saturday.
Barry Thompson, chair of March4Justice which organised the event, said: "There were some very emotional scenes, especially when the families gave the boxes of petitions in to 10 Downing Street.
"We have had so much support from people in Liverpool, the UK and we have also have 480 letters of support from 67 different countries worldwide.
"Those who lost their loved ones said it was a positive thing handing in papers showing so much support for their plight.
We were shocked and delighted we heard the documents would be released but we don't want to be waiting for years, we have already had to wait two decades
Jenny Hicks, who lost her two daughters at Hillsborough
"We gathered 40,000 signatures in just seven weeks, it has been a mad time.
"Let's just hope this encourages the government to realise its obligation to the families of the 96, the fans, the club and the city [Liverpool] as a whole."
The campaigners also want the release of some 300 boxes of information about the tragedy.
Ms Hicks added: "This march helped increase the pressure on the government to take some action.
"We were shocked and delighted when it was agreed that the documents should be released but we don't want to be waiting for years, we have already had to wait two decades.
"At the moment it's a waiting game, we just hope this march will have helped make a difference."
Crushed to death
The marchers also want any new investigation to recognise that not all the victims had died by 1515 BST on the day of the disaster.
It was the cut-off time imposed during the original inquest into the deaths.
Earlier this year, former Home Secretary Jacqui Smith asked South Yorkshire Police to release the 300 boxes of information it holds.
And calls for a further investigation were backed by former Culture Secretary Andy Burnham.
The 96 fans were crushed to death in the Leppings Lane end of the Sheffield stadium during Liverpool's FA Cup semi-final with Nottingham Forest.
South Yorkshire Police opened a large exit gate which forced too many Liverpool fans on to the terrace, leaving the fans inside trapped between people entering the ground and the metal fences at the front of the stand.
Families of the victims have continued a two-decade long campaign for a full inquiry into the disaster.
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