A gang of men and boys convicted of sexually abusing teenage girls in Peterborough used "sophisticated" tactics to groom their victims, detectives have said.
They befriended vulnerable girls, gave them gifts, money, drugs and alcohol and used violence and intimidation to control them, subjecting them to "appalling" abuse in places such as children's playgrounds.
Two men and three teenage boys were found guilty of a series of rapes and sexual assaults on five girls.
Their convictions were the result of a "victim-led" investigation, involving Cambridgeshire Police, Peterborough City Council children's services and other agencies.
It formed part of a wider investigation, called Operation Erle, into allegations of sex abuse by other groups of men and boys against young girls.
Police are hopeful of further charges and trials.
"A large team of officers, social workers and police staff are dedicated to the over-arching investigation," said Det Supt Gary Ridgway, who is leading the operation.
"We are working closely together to support the victims we are speaking with and to bring offenders to justice as quickly as possible."
Detectives stress that the investigations are not being linked by offenders or victims, only by the fact that they all involve young people being exploited.
Det Supt Ridgway said: "We decided to carry out an information trawl to identify young people who were potentially vulnerable and at risk of being exploited.
"At that stage we had no complaints, nor any suggestion that such exploitation was going on in the city."
He said officers won the trust of the young people, some of whom later revealed they had been abused.
They had not all been previously known to police or social services.
Their abusers called themselves the Peterborough Mally Gang - a Czech phrase meaning "young gangsters" - and congregated at a fried chicken shop in the city.
Police, however, considered them a loosely affiliated group rather than a traditionally-defined criminal street gang.
Hassan Abdulla, 33, recruited the others to deal marijuana. He has been convicted of drugs offences in the past.
There were five victims, aged 13 and 14. Most of the offences took place between May and December 2012, but some occurred last May and one offence dates back to 2011.
The jury at the Old Bailey heard one of the victims, known as Victim A, had learning difficulties. She was tied up, raped and sexually assaulted by a number of men in a playhouse at a Peterborough park.
"It's an appalling crime," said Det Supt Ridgway.
"We've got young people who, because of their experiences and their learning disabilities, are really not in a position to protect themselves or take control of their lives in many instances, and that's terribly exploited by some really evil, unpleasant people."
Police said they considered the grooming techniques used in this case to be "sophisticated" because Zdeno Mirga groomed one of the girls to believe she was his girlfriend, before prostituting her to his associates.
Det Supt Ridgway said the biggest challenge for police and other agencies was winning the trust of the young people they spoke to.
"The victims have endured horrific abuse and the legacy of that will, no doubt, stay with them for the rest of their lives."
He said they had shown great courage in speaking to officers and social services.
"I have nothing but admiration for the way they have conducted themselves throughout this traumatic ordeal, especially going to court and giving evidence against those who abused them," he said.
"They have already made great steps in moving on with their lives and putting the horrific experiences behind them, and we are committed to helping them continue to rebuild their lives."
Stewart Jackson, Conservative MP for Peterborough, said: "There are bigger lessons that we have learned in Oxford and in the north-west of England and we're learning in Peterborough.
"I think we have got better at dealing with these young people who might fall through the cracks of care and the duty of care that the state has.
"Thankfully, Peterborough City Council and other agencies acted quickly but there are always lessons to be learned."