A surgeon is to face a criminal inquiry over allegations about his treatment of more than 1,000 breast cancer patients.
West Midlands Police said they were liaising with the Crown Prosecution Service to determine the course of the investigation into the conduct of Ian Paterson.
Mr Paterson is alleged by a law firm representing some of his former patients to have performed up to 1,150 "unnecessary, inappropriate or unregulated" operations.
Thompsons Solicitors, which is pursuing negligence claims for several women, said Mr Paterson worked at a number of NHS and private hospitals from 1994, including those run by Heart of England NHS Foundation Trust, which covers hospitals in Sutton Coldfield, Solihull and Birmingham.
An investigation into Mr Paterson by the General Medical Council potentially spans up to 700 cases of an unregulated procedure that involved leaving some breast tissue behind after a mastectomy, Thompsons said.
It is further alleged that up to 450 women could have had invasive breast surgery when a biopsy might have been sufficient.
The Medical Defence Union said in a statement: "Mr Paterson is co-operating fully with the GMC investigation. He cannot comment further due to his duty of patient confidentiality and the ongoing investigation."
Sky News' Health and Science correspondent Thomas Moore said the GMC has been looking into Mr Paterson for some time, adding that conditions were imposed on his practice in July 2011.
Mr Paterson's GMC record shows that the Interim Orders Panel ruled that he "must not carry out breast surgery" and that he should "confine his medical practice ... to general surgical work and out-patient consultations with patients with breast disease".
Kashmir Uppal, a senior medical negligence solicitor at Thompsons, said she believed patients had been subjected to needless worry and risk.
She said the law firm was also liaising with the GMC to assist its investigations.
"The women who have come forward so far have been very brave," Ms Uppal said.
"Hopefully all who have had unnecessary or inappropriate treatment will seek reassurance or justice."
In a statement confirming the police inquiry into Mr Paterson, who has not been arrested, Detective Chief Inspector Matt Markham said: "West Midlands Police can confirm it has received a referral from the General Medical Council in relation to allegations about the medical practices of a surgeon who previously worked in Solihull.
"A criminal inquiry has been launched and the force is working closely with the Crown Prosecution Service to determine the course of the investigation."