Northumbria Police has confirmed the incident has been referred to the Independent Police Complaints Commission due to the contact between officers and the man before he died.
Officers were in the process of arresting a second man in connection with the disorder when the prisoner inside the police vehicle escaped and ran off from officers.
Enquiries were carried out to locate him and at 1:03am his body was found at the bottom of Marsden Grotto cliffs.
– Northumbria Police
The air ambulance was called and the man was given CPR treatment by officers until paramedics arrived. Despite efforts to save him, he was pronounced dead at the scene. The area around the cliffs has been cordoned off while an investigation is carried out.
Liberal Democrat leader Nick Clegg has told Daybreak his party did not "contest seriously" last week's by-election in South Shields, in which its candidate topped only the Monster Raving Loony Party.
The Deputy Prime Minister said: "There was a by-election just a few weeks ago in Eastleigh which we spectacularly won. Some by-elections parties do well in others they don't contest seriously. That was clearly the case if you contrast Eastleigh with South Shields."
Mr Clegg also said his party would not "lurch (to the) right or left" after its disastrous local election results, which saw it lose 124 council seats and comfortably trail UKIP.
Labour's election co-ordinator Tom Watson said his party enjoyed a good night in the local elections and South Shields by-election.
Speaking to the BBC Radio 4 programme, Mr Watson said "We had a good result on what we have seen so far, to get 50 per cent of the vote in South Shields, to win back the mayor in Tyneside, to make progress in the Westminster battleground seats within counties is good for us.
"In the Westminster battleground seats, places like Harlow, Hastings, Stevenage, Cannock, the Westminster seats we lost in 2010 and we need to win back in 2015, they are coming back to Labour in quite big numbers."
The MP for West Bromwich East said Labour leader Ed Miliband had been consistently told by voters that they felt a sense of "powerlessness" when it came to politics and its ability to change their lives.
"At the heart of this is economic failure, they feel the Government plan is not working and they feel the job of the Labour Party is to convince people there is a better way, that we can address this squeeze on living standards and give people more hope," he said.
The only "real choice" for voters at the forthcoming local elections is between the Conservatives and Labour, David Cameron has said.
In a direct attack on Labour leader Ed Miliband's policies, the Prime Minister said "the scale of the challenge is actually laid bare today because this is the day when the leader of the Labour Party is turning left.
"More spending, more borrowing, more debt - that is what he's calling for, more of all of those things that got us into this mess in the first place."
Mr Cameron said the Conservatives were "fighting for the pound in your pocket" adding it was "a moral imperative" to keep council tax down.
"We're fighting to keep it there because we get something, it is your money, not our money and not Government money."
Nelson, standing for Lee Nelson's Well Good Party read out a speech on the steps of the Town Hall in South Shields, delivering a "17-point manifesto for a Well Great Britain" with a series of eye-opening policies, including issuing each child with lottery scratch cards at birth.
He added: "David Cameron, George Osborne, Boris Johnson - I wasn't educated at Eton or Oxford. In fact, I wasn't educated at all. It's time to give the posh the push. And let Lee be your leader for a well great Britain."