Fifteen arrested over conspiracy to rape in Newcastle
Thirteen men and two women have been arrested in Newcastle on suspicion of conspiracy to rape.
Northumbria Police said 13 properties in the city had been searched as part of Operation Sanctuary.
A force spokesman said the inquiry involved allegations of sexual assault involving teenage girls and young women - some in the care of the local authority.
The city council said it was working with police to help alleged victims.
Council leader Nick Forbes said the authority was informed about the investigation a week ago and he was "shocked and appalled" by the allegations.
Temporary Assistant Chief Constable Gary Calvert said: "This is a sensitive investigation which is at a very early stage and moving rapidly.
"I understand that these types of allegations can cause the public concern and I want to reassure the community that police take crimes of this nature extremely seriously and will thoroughly investigate them.
"Our overarching priority is to protect any victims or potential victims and to bring any offenders to justice."
Mr Forbes said that those arrested were from various parts of the city.
"There is absolutely nothing to suggest the alleged offenders are from any one community - they are from a range of backgrounds, range of communities and range of areas of the city, but inevitably events like this do raise people's concerns", Mr Forbes said.
"But it is important to point out that the alleged victims and offenders were known to each other."