More than 140 people have told police investigators that they were sexually or physically abused at a young offenders centre between the late 1960s and mid-1980s.
Since August, when detectives announced that they were re-opening a decade-old investigation into allegations against staff working at Medomsley Detention Centre near Consett, County Durham, 143 people have come forward.
Investigators said they were left “shaken” by the “horrific” accounts they heard, but praised the courage of the alleged victims.
Young inmates at the centre were so desperate that they asked each other to break their legs so they could be moved elsewhere and escape the staff, the BBC has been told.
Ray Poar, who was 17 when he was imprisoned for stealing biscuits from a factory, has waived his right to anonymity.
He told the BBC how he was woken up and made to bunny-hop to the showers after wetting his bed. When he couldn’t make it, he was kicked, he said.
He said: “The odd punch in the arm, the ribs, the back of the knees, every day they were doing it. You had nobody to talk to.”
“It's always in my head, the shame, it's ruined my life, it's completely ruined it,” he added.
Many of those sent to Medomsley were first-time offenders often detained for relatively minor offences.
Detective Superintendent Paul Goundry, of Durham Constabulary, said: "We said from the outset this was going to be a long and complex investigation which we fully expect will last at least another 12 months.
“The accounts we have heard have been horrific and have shaken some very experienced detectives who are working on this.
"It is obviously distressing to hear from so many victims, but at the same time I am relieved they have shown the confidence in us to get in touch and allow us to help them.
“Our efforts are directed not just at establishing what happened in Medomsley over that period but ensuring the victims are left in a better place and get the support and advice they need.”
In 2003, a separate police investigation called Operation Halter led to the conviction of Neville Husband, a prison officer at the centre.
Mr Husband was initially jailed for eight years after being found guilty of abusing five young people.
The publicity surrounding the trial then led to others coming forward and Husband was subsequently jailed for a further two years for these attacks.
Leslie Johnson, a store man, was sentenced to six years in 2005.
Both men have since died.
Additional reporting by PA