LONDON: More than 450 patients died at a hospital in England after being given strong painkillers without “medical justification”, a report found Wednesday.

An independent panel led the investigation into the deaths between 1989 and 2000 at the Gosport War Memorial Hospital in the southern city of Gosport. “The hospital records to which the panel has had privileged access demonstrate that 456 patients died through prescribing and administering opioids without medical justification,” the commission, led by former Liverpool bishop James Jones, said in a statement.

It added that taking into account missing records, another 200 patients may have died as a direct result of the “institutionalized practice” of administering powerful drugs. The report said that Dr. Jane Barton had been “responsible for the practice of prescribing which prevailed on the wards”.

The documents showed that several nurses raised concerns about the prescribing of diamorphine in the early 1990s, but their warnings “went unheeded”, according to the panel. “The opportunity to rectify the practice was lost, deaths resulted and 22 years later it became necessary to establish the panel in order to discover the truth of what happened,” it said.

British Prime Minister Theresa May called the findings “deeply troubling”, saying the deaths had “brought unimaginable heartache to the families concerned”.