STOCKHOLM (Reuters) - The reputation of the Karolinska Institute, one of Sweden’s top hospitals that awards the Nobel prize for medicine, has been badly damaged by allegations patients died as a result of a surgeon performing experimental operations without clearance, an official report said.

A general view of the Karolinska hospital in Stockholm, Sweden, January 10, 2012. REUTERS/Anders Wiklund/TT News Agency /File Photo THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. SWEDEN OUT. NO COMMERCIAL OR EDITORIAL SALES IN SWEDEN. NO COMMERCIAL SALES

Criticism of the Karolinska Institute, which had employed Italian surgeon Paolo Macchiarini, led to the resignation of the secretary of the Nobel Committee at the Institute in February and to calls for the award to be scrapped this year and next.

Bjorn Hurtig, a Swedish lawyer who represents Macchiarini, could not immediately be reached for comment on the report. In the past, Macchiarini has denied any wrongdoing.

Macchiarini was fired in March when Karolinska said he had supplied false information on his CV and was guilty of scientific negligence after two of his patients died. Swedish prosecutors are investigating Macchiarini on suspicion of gross criminal negligence leading to another person’s death.

“Patients have been injured, even died,” said Kjell Asplund, head of the Swedish National Council on Medical Ethics, who headed the investigation commissioned by the institute.

“Employees have suffered as has clinical research as a whole. What is needed are long term, wholehearted efforts to restore trust.”

In February this year, Karolinska launched a fresh enquiry into misconduct allegations, leading four professors at the Nobel Academy to step down from the prize committee while it proceeded.

Bo Risberg, former head of the ethics committee at Karolinska, has called for the Nobel medicine prize to be put on ice for two years and for prize money to be used to compensate the relatives of the patients Macchiarini operated on.

A world-renowned surgeon, Macchiarini was employed as a researcher into stem cell biology at the Karolinska Institute and consultant at Karolinska University Hospital in 2010.

The investigation centered on three operations conducted between 2011 and 2012 in which Macchiarini transplanted synthetic tracheas coated with stem cells into patients.

Asplund said Macchiarini performed the operations before sufficient study had been done on the procedure and that the operations could not be justified on the grounds of being life-saving.

Two of the patients have since died while the third remains hospitalized.

“The investigation has highlighted serious mistakes in the way the three patients were treated and serious flaws in the hospital’s routines, system and culture,” hospital director Melvin Samsom said in a statement.

In 2014, Macchiarini was accused of scientific misconduct by colleagues who claim he presented too uncritical an interpretation of the results of his research. After an internal investigation Karolinska cleared him from the allegations.

Karolinska also investigated allegations published in Vanity Fair that he had lied on his CV. It concluded that the document contained several falsehoods, “although none so serious as to justify his dismissal or resignation”.