A hospital probe over damaged vials containing an opiate drug 50 times stronger than heroin has found the problem was likely a manufacturing fault.

The James Paget University Hospital in Gorleston had questioned theatre staff after eight incidents of damaged or broken fentanyl vials being found during 2020.

A letter at the time to staff said it was most likely that the fentanyl vials were being tampered with to either cause disruption, gain financially or for personal use.

The hospital trust asked staff if they believed a colleague was acting strangely and showing signs of fentanyl side effects or withdrawal symptoms and that the police could be called in.

But now hospital chiefs have now admitted that the likely cause of the damaged vials was a manufacturing fault.

Bosses are writing to all those involved in the investigation to thank them for their support during what they call a "difficult and necessary process".

A statement from the hospital said: “Last year, the trust’s monitoring of controlled drugs and safety procedures picked up an increased incidence of unexplained damage to vials containing fentanyl.

"Any incident involving a controlled drug must be reported and an investigation was opened to look into this increase in more detail.

"As part of this investigation staff in the area concerned were initially written to and given details about how they could safely come forward with any information they thought might be relevant, should they wish to, and to ensure they knew that support was available.

"Several members of staff were also interviewed during the course of this enquiry, as the trust takes all medication related incidents very seriously, and it was important to determine what had happened.

"The investigation considered a number of options that may be at the root of the increase of the incidents, including the possibility of a manufacturing fault.

"After information was obtained from the manufacturer, it was determined that this was the most likely explanation for the incidents as no evidence of the misuse of controlled drugs was found.

"We recognise that this investigation has had an impact on our staff. A letter is being sent to all of those affected which will thank them for their support during this difficult but necessary process.”