Police have named the fifth patient whose death at the hospital at the centre of sabotage allegations is being investigated by police.
Vera Pearson, 84, died on July 14 at Stepping Hill Hospital in Stockport, Greater Manchester.
Her case was referred to detectives by a coroner earlier this week because of her low blood sugar level.
Police say saline solution at the hospital was contaminated with insulin, which can cause low blood sugar.
The pensioner's family said they wanted to be left alone to grieve in peace.
She was not among the tally of 14 patients who police initially believed had been affected by a batch of 36 saline vials sabotaged with insulin.
Police are also looking at the suspicious deaths of Tracey Arden, 44, Arnold Lancaster, 71, George Keep, 84, and Derek Weaver, 83.
Detectives have until 9.05pm tonight to question Stepping Hill nurse Rebecca Leighton, 27, on suspicion of murder before they must decide whether to charge her, release her from custody or apply for extra time to detain her - possibly up until Sunday morning.
On Wednesday, officers arrested Miss Leighton at her flat in Heaviley, Stockport, which is a mile away from the hospital.
The alarm was raised last week when an experienced nurse reported a higher than normal number of patients on her ward with "unexplained" low blood sugar levels, pointing to saline containers being sabotaged.
Police found the contaminated batch in a store room close to wards A1 and A3 of the hospital.
It was reported today that South Manchester Coroner John Pollard will now review all deaths at the hospital since July 7, with all future deaths also referred to him.
Greater Manchester Police has admitted it was "likely" it will be asked to investigate further deaths by the coroner.
Assistant Chief Constable Ian Hopkins said it was part of the coroner's "belt and braces approach" to ensure that all cases with potential links to the inquiry were appropriately investigated and scrutinised.
He added there had been no further incidents of deliberate contamination at the hospital since the police were called in and security was stepped up.
Detectives continue to focus on preventing further harm at the hospital and once that is done they will look at any cases before July 7.
Mr Weaver, from Stockport, died yesterday after suffering a hypoglycaemic episode on July 11 - a day after he was admitted from his interim care home with breathing problems.
Multiple sclerosis sufferer Ms Arden, of Heaviley, died on July 7. Retired photographer Mr Lancaster, of Romiley, died on July 11, while Mr Keep, of Cheadle, died on July 14 after being admitted to the hospital with a broken hip.
The results of further pathology tests to find out if insulin contributed to the fatalities are still awaited and the families involved have been forced to postpone funerals.
A man in his 40s, who was part of the original pool of 14 patients thought to have been affected, remains "very poorly" in a critical care unit at Stepping Hill.
Nine other patients are thought to have recovered from their symptoms.