Hundreds of potential suspects have been identified in an investigation into child sex abuse in Rotherham, along with several thousand new lines of enquiry, police have said.
The National Crime Agency began an investigation in December last year following the Alexis Jay report that revealed there were 1400 victims of abuse in the town between 1997 and 2013. Police and other authorities knew about the abuse, but failed to act.
Police said Wednesday that "stage one" of their investigation had uncovered "a significant number of potential offenders. The current figure is in the low hundreds".
The officer in charge of the investigation, NCA Director Trevor Pearce, said: “It is clear that some details provided will be duplicates of other details, names, nick-names or street names. Others may not prove to be offenders at all, or may be witnesses to abuse.
“The information established from these reports will form part of the investigation and it will be some time before we are able to put a more precise figure on the number of people who have been involved, directly or otherwise, in the grooming and sexual exploitation of children."
Mr Pearce said police had undertaken a "massive information gathering exercise" in the last six months and had taken possession of nearly 1,500 files, which had to be indexed, read, assessed and entered into a Major Incident Room system.
He said: “This will enable us to identify links to information from other sources and within other investigations. Last week alone, we took possession of a further 45 boxes of material that will also now be assessed."
Steve Baldwin, who is a Senior Investigating Officer involved in the operation, said police now had more than 3,300 lines of enquiry.
He said the abuse was "horrific" and the evidence police had gathered "details some very disturbing events".
Police believe the 1,400 victims identified in the Alexis Jay report remains a "very good assessment" of the numbers of children abused during the time period.
Mr Baldwin said: “We will prioritise action against suspects who may continue to pose any risk of harm today and those who have caused most harm in the past. We will examine all allegations of abuse and, most importantly, we will listen to victims.
“I know that there are more victims yet to be identified and for us to reach out to. Progress will be best achieved at present by tackling what we have now and demonstrating through our actions that we deserve the trust and confidence of others,” said Mr Baldwin.
The NCA is working with South Yorkshire Police, Rotherham Metropolitan Borough Council, local health agencies, the Office of Police and Crime Commissioner and others to unravel the unresolved cases.
At present the operation has 32 officers working on it, but that is expected to increase in the coming months, the NCA said.
A review of three existing South Yorkshire Police investigations into sex abuse are also taking place and will be published in April.
Last month two new reports revealed that authorities in Rotherham had been warned about child sexual exploitation in 2003 - and given a list of the suspected main offenders - and told three years later that the problem was established and very serious, but had failed to investigate.
Dr Angie Heal provided a list of potential abusers as part of a report on the links between grooming and drug dealing in 2003 to police and council officials. That report and another from 2006 were released under the Freedom of Information Act to The Sheffield Star.
Dr Heal, who has since left the police, said she had "no idea" whether any of the suspects she tipped her bosses off about were ever convicted.
Last year, an inquiry found 1,400 children were abused by gangs of men, mainly of Pakistani origin, in South Yorkshire between 1997 and 2013.
The inquiry concluded: "It is hard to describe the appalling nature of the abuse that child victims suffered."
Last years report found that in more than a third of the 1,400 cases the youngsters were already known to child care agencies. Girls as young as 11 had been raped by large numbers of men.
The inquiry said there had been "blatant" collective failures by the council's leadership.
Professor Alexis Jay, who wrote the report, said she found examples of "children who had been doused in petrol and threatened with being set alight, threatened with guns, made to witness brutally-violent rapes and threatened they would be next if they told anyone".
Prof Jay said: "They were raped by multiple perpetrators, trafficked to other towns and cities in the north of England, abducted, beaten and intimidated."
The two new reports provided further damning evidence of the police and council's failures.
In the first report Dr Heal warned in 2003 that there was no room for complacency over the allegations. However, three years later she had to prompt police to act again, telling authorities the problem was established and serious.
Both reports went to senior police officers and council officials but nothing was done.
Dr Heal told the BBC: "I just cannot fathom it at all as to why no action, no concerted action was taken."
She added: "It meant that a significant number, over 1,400, continued to be abused, assaulted, raped, their families devastated by what happened."
Dr Heal said that the authorities failure to act "makes me really angry and upset".
The Star reported that police not only failed to act, but when they were finally spurred into action, they were so slow key opportunities to crack the case were missed.
Citing the released reports, it said one man had told police that a significant number of teenage girls had been visiting his neighbour's house, and that he had offered his residence as an observation post. Police took seven months to get back to him, by which time the suspected abuser had moved. In another case a teenager told police she had been raped by a "well-known heroin dealer", only to be charged with theft herself. A rape investigation was never launched.
South Yorkshire Police and Crime Commissioner Alan Billings told the BBC that agencies knew about Dr Heal's reports at the time but were focusing on other issues.
He said her reports were "utterly shocking", saying when you read them there's "no holds barred".
Mr Billings laid the blame beyond police and council officials, saying Dr Heal's reports also went to safeguarding boards and the national government, "it was widely known what she said".
He said: "I think there are more people that have questions to answer than the police. The only sense I can make of it is that at that time, police were prioritising other things like burglary and car theft. I don't think anyone understood what grooming was."
In a statement, South Yorkshire Police admitted to past failings and pointed to an ongoing investigation by the Independent Police Complaints Commission into misconduct issues.
It said it had made "significant progress" in tackling child sexual exploitation but understood more "needs to be done".