Police are investigating the deaths of patients at a hospital in Brighton.
Detectives are looking into allegations of medical negligence at the Royal Sussex County Hospital over a five-year period. The number of deaths is around 40.
The claims concern alleged failings in neurosurgery and general surgery.
The claims of medical negligence were made by two consultant surgeons who lost their jobs after blowing the whistle about patient safety, The Guardian reported.
Officers from Sussex Police last week wrote to the trust's chief executive George Findlay, confirming they had launched a formal investigation into "a number of deaths", according to the newspaper.
Police were investigating allegations of "criminal culpability through medical negligence" made by "two separate clinical consultants" at the trust, a letter reportedly said.
Both whistleblowers claimed the trust failed to properly investigate the deaths, which took place between 2015 and 2020, and learn from mistakes made, the newspaper added.
Inspectors from the Care Quality Commission downgraded the trust last month and it was given a 'requires improvement' rating for patient safety.
A trust spokesperson said: "The trust has been contacted by Sussex Police as part of their inquiries relating to the care of a number of general surgery and neurosurgery patients at the Royal Sussex County Hospital in Brighton between 2015 and 2020.
"It would be inappropriate to comment further at this stage other than to confirm that we are co-operating fully to ensure the concerns raised are investigated."
A Sussex Police spokesperson said: "Sussex Police has received allegations of medical negligence at the Royal Sussex County Hospital, Brighton, and is currently assessing these allegations.
"The concerns raised relate to neurosurgery and general surgery in a period between 2015-2020.
"Inquiries are at an early stage and this does not necessarily mean this will lead to criminal prosecution.
"We are working closely with partner agencies and the hospital trust is co-operating fully with our review."