A seven-year-old boy died after vital equipment at a private hospital needed to monitor his sleep apnoea was switched off, a report says.
James Dwerryhouse suffered brain damage as a result of cardiac arrest following an operation at Portland Hospital in central London on 25 August last year.
A serious incident report found the equipment monitoring him overnight was turned off for almost three hours.
The hospital said it was "co-operating with all investigations".
Police have said his death is "deemed to be non-suspicious".
James suffered from numerous health conditions including sleep apnoea which can cause life-threatening stoppages in breathing.
He had been in hospital for an operation to create a colostomy bag.
The operation was a success but he was later found unresponsive in his bed at the private hospital's paediatric intensive care unit.
He was transferred to the Treehouse Hospice in Suffolk but died the next day.
The hospital's report found the root cause of James' death "appears to be the removal of vital signs monitoring between 01:15 and 03:58, as this resulted in the inability to be alerted to a suspected deterioration in the child's respiratory condition and reducing oxygen saturations."
The report also found hospital staff working that night:
- Removed the monitoring equipment without consulting a more senior member of staff
- Had longer breaks during the night shift than hospital rules permitted
- Failed to properly document their observations of James during the night
- Immediately turned off sounding alarms when they reconnected James' monitoring equipment
James's family have launched legal action against HCA Healthcare UK, the owners of Portland Hospital.
His mother Marguerite called her son's death "completely heart-breaking".
"Only days earlier, he'd been to a summer club and he'd been chasing around, up and down the slides and having a great time," she said.
A Portland spokesman said the hospital is "co-operating with all investigations, and we are unable to comment further until they are completed."
A statement from Scotland Yard said officers "are undertaking inquiries on behalf of the coroner".
"The death is deemed to be non-suspicious. No one has been arrested," it said.
An inquest has yet to be held, solicitors for the family have said.