Detectives believe they have smashed a child trafficking gang in Oxford preying on runaways as young as 11 for Britain's sex trade.
Thirteen men were arrested in the city by police investigating claims 24 vulnerable girls under 16 were groomed for rape.
Officers suspect gang members targeted children in care or living rough and transported them around Britain over a six-year period.
Thames Valley Police said nine men - aged between 21 and 37 - remain in custody and are being quizzed over a string of offences, including causing the prostitution of females under the age of 18, administrating drugs for the purpose of rape, trafficking, grooming and rape.
Four men, aged 23, 31, 34 and 37, were released on bail until April 19.
Detective Superintendent Rob Mason said: "We believe we have uncovered an organised crime group who have been running a business of selling young girls for sex. We have also identified a number of customers who we have reason to believe have used this service."
More than 100 officers took part in raids as the force executed 14 warrants across the city as part of an operation named Bullfinch.
Police were not willing to comment on the nationalities of any of the suspects but sources said many of the offences centred in or around the Oxford area.
Police suspect they have arrested both those behind the running of the network and the men that have paid for sex. Detectives are keeping an "open mind" as to whether there would be further arrests.
Officers are working closely with children's services, the Child Exploitation and Online Protection Centre and other forces that have been through similar investigations. Police are also urging anyone who thinks they may have been a victim to contact ChildLine.