Three former Greater Manchester Police senior officers are being investigated by The Independent Office for Police Conduct (IOPC) over their actions and involvement in Operation Augusta.
Operation Augusta was a 2004 investigation into child sexual exploitation by grooming gangs in South Manchester.
The investigation was prompted by the death of Victoria Agoglia, 15, a girl under the care of Manchester City Council, who reported being raped and injected with heroin by a 50-year-old Asian man.
Earlier this year a review of the investigation, published by Greater Manchester Mayor's Office, found that victims of the gangs were "failed" by Greater Manchester Police.
The review also raised concerns about the conduct and decision-making of some of the officers involved.
GMP referred themselves to the IOPC in February.
The watchdog said that they have since sought further information from the force and have now begun an investigation into three former senior officers actions in the "supervision and setting of direction" in Operation Augusta.
Two of the officers are said to be retired, whilst another is currently working for another organisation.
IOPC Director of Major Investigations Steve Noonan: "This has been a lengthy but necessary process, and it has taken some time to gather the information required to make a decision whether it was necessary to investigate, and who should conduct the investigation.
"The Mayoral review raised many questions about the actions of those involved in Operation Augusta. We have now decided it is necessary to investigate the individual conduct of these three former GMP officers who were all involved in either supervising or setting the direction of Operation Augusta.
"Though the content of the Mayoral review has been analysed as part of our decision to begin an investigation, it was not a specific investigation into the actions of the officers involved. We now need to establish and examine all the available evidence. The investigation is in its early stages."
Andy Burnham said:
Deputy Chief Constable Ian Pilling, said: "Following the publication of the CSE Assurance Report in January 2020, GMP voluntarily referred its role in Operation Augusta to the Independent Office for Police Conduct.“Since making the referral, we have worked to cooperate fully with the IOPC and provide all the relevant and necessary information for them to make their assessments. We acknowledge their decision to independently investigate this matter and will continue to support their investigation in any way possible. “It would be inappropriate for us to comment on this matter further whilst an independent investigation is ongoing, but I would like to take this opportunity to reassure the public that child sexual exploitation remains a top priority for GMP."
Greater Manchester Police are encouraging any victims of child sexual exploitation to contact them on 0161 856 2124 or via email@example.com.