Rebecca Leighton, 27, has been named as the nurse arrested on suspicion of murder by police investigating the deaths of three patients at Stepping Hill Hospital in Greater Manchester.
Three people have died at Stepping Hill after their saline drips were tampered with: Tracey Arden, 44, George Keep, 84, and Arnold Lancaster, 71. One other man in his 40s remains critically ill. In total 14 patients have been affected.
Rebecca Leighton, 27, has been named by sources as the woman under arrest.
Detectives believe insulin was injected into saline containers, which were used in intravenous drips in at least two wards in the hospital.
Dr Chris Burke, Chief Executive Stockport NHS Foundation Trust said: “We are aware that Greater Manchester Police have made an arrest this morning of a 27-year-old female.
“As the police are continuing with their enquiries we are unable to provide any further details but it is important to stress that no charge has been made at this stage.”
Ambulance admissions to Accident and Emergency are being diverted to other hospitals and visiting has been restricted on one of the affected acute wards.
Detectives were called in after an experienced nurse reported a higher than normal number of patients on her ward with “unexplained” low blood sugar levels, pointing to the saline solution being sabotaged with insulin.
Officers found insulin had contaminated a batch of 36 saline ampoules in a storeroom close to ward A1.
The three deaths remain unexplained as detectives await the results of further pathology tests to find out if the insulin contributed.
Inquests into the deaths were opened and adjourned by South Manchester coroner John Pollard yesterday.
Mr Hopkins told reporters at a press conference at the hospital on Tuesday that the police investigation “at the moment” was concentrating on the 14 patients who may have come to harm.
Police said that a product containing saline solution that was found damaged in the maternity ward at Stepping Hill had not been contaminated. Preliminary tests confirmed no trace of any substance.
Assistant Chief Constable Ian Hopkins, leading the inquiry for Greater Manchester Police, said: “It is important to stress that this product has not been contaminated and, in fact, the damage could very well be accidental, as can happen quite easily in a busy hospital environment.
“Extra security measures are in place across the hospital and staff continue to be vigilant, which of course is to be expected.
“Due to heightened awareness, staff are alerting police to anything they feel might be suspicious or relevant to the investigation and to date there has been no further contamination of any product since the control measures were introduced.”