Police investigating suspicious deaths at an English hospital say they are working flat-out, with 60 detectives on the case.
Ian Hopkins, assistant chief constable of Greater Manchester Police, said the thoughts of officers were with the family of Tracey Arden (44), George Keep, (84) and Arnold Lancaster (71) who died at Stepping Hill Hospital in Stockport.
The deaths of all three are being linked to the deliberate contamination of saline solution, with the hospital now at the centre of an intense police investigation.
There has been growing speculation that several more deaths may be looked at and that the contamination could have taken place outside the hospital. Insulin was found in a batch of 36 saline ampoules in a storeroom at the hospital.
The 11 people who survived the effects of the tampered medication will also be interviewed.
Detectives believe the insulin was deliberately injected into the saline containers which were used in drips in at least two wards, but they say the three deaths remain unexplained as they await post-mortem examination results.
Mr Hopkins said: "Our thoughts continue to be with the families of Tracey Arden, George Keep and Arnold Lancaster. The anguish they will be feeling at this time must be terrible.
"I would like to reassure them we are doing all we can to find out what caused the death of their loved ones.
"There is an ongoing complex investigation requiring detailed forensic analysis and we are continuing to interview a large number of witnesses.
"We are working closely with hospital managers to minimise disruption to the running of the hospital, but ultimately our duty is to those who have died and their families to conduct a thorough investigation into their deaths.
"We are also working to reduce the risk of harm to others being cared for at Stepping Hill."
The family of Mr Keep said they feared more patient deaths would be investigated.
A patient with lung cancer, Mr Keep died at Stepping Hill Hospital two days after a ward nurse raised concerns about a higher than normal number of patients with unexplained low blood sugar levels.
The pensioner, from Cheadle, was admitted to Stepping Hill on June 27 after he suffered a broken hip in a fall.
He was operated on and was recovering well until two days before his death when his blood pressure and blood sugar levels started to drop, said his daughter Carolyn Knowles.
Long-term multiple sclerosis sufferer Ms Arden, a mother-of-two, died on July 7, while Mr Lancaster died last Monday.
Police are continuing to interview doctors, nurses, porters, patients and visitors, while security remains high in and around the hospital.
South Manchester coroner John Pollard is due to open inquests on all three deaths today.