A hospital and one of its managers are facing a criminal investigation into the death of a vulnerable man who absconded by climbing a fence.
An inquest concluded failings amounting to neglect contributed to the death of Matthew Caseby in 2020, after he fled from Birmingham's Priory Hospital Woodbourne and was hit by a train.
The investigation will be carried out by the Care Quality Commission (CQC).
Priory said it would co-operate fully "if enquiries are raised by the CQC".
Mr Caseby, 23, climbed over a 2.3m-high (7ft 6in) courtyard fence on 7 September 2020.
He was found dead the following day after being hit by a train near Birmingham's University station.
The inquest in April heard other patients had previously climbed the fence and, despite concerns by members of staff, no action was taken to improve security in and around the courtyard until another patient absconded two months after Mr Caseby's death.
The jury was told the personal trainer, who was an NHS-funded patient at the private hospital, should have been under constant observation, but was left unattended for several minutes.
Following the inquest, coroner Louise Hunt said she was concerned the fence and courtyard area may still not be safe and urged health chiefs to consider imposing minimum standards for perimeter fences at mental health units.
She also criticised record-keeping and how risk assessments were carried out.
A spokesperson for the CQC watchdog said it was conducting "a formal criminal investigation" in relation to the death "to establish whether a criminal offence has been committed by the provider and registered manager".
They added: "That investigation is currently ongoing and we will report further as soon as we are able to do so."
Mr Caseby, who lived in London, was originally detained under the Mental Health Act following reports of a man running on to railway tracks near Oxford on 3 September.
His father, Richard Caseby, 61, said: "The catalogue of failings that led to Matthew's death was horrifying."
He added: "All I've ever wanted to do is to expose the truth and stop this from happening to anyone else."
A Priory spokesperson said: "Consistent with its statutory powers, CQC investigates a substantial number of patient incidents in the UK.
"Priory and its employees will co-operate fully if enquiries are raised by the CQC with regard to the care of Matthew Caseby and it would not be appropriate to comment further at this time."