A nurse who was charged with the murder of three patients in West Yorkshire may have killed more, police have said.
The offences are said to have been committed between 2000 and 2002
Anne Grigg-Booth, 51, of Nelson, Lancs, was due to go on trial for the murder of three women aged 96, 75 and 67, at Airedale General Hospital in Keighley.
On Monday her body was found at her home. Police, who are not treating her death as suspicious, say they have looked at other deaths at the hospital.
Ms Grigg-Booth, a mother of one, always denied responsibility for any deaths.
Detectives said they had looked at a number of deaths at the hospital, where Ms Grigg-Booth had worked for 25 years, and found some suspicious cases.
Ms Grigg-Booth was charged in September 2004 and was due to next appear in court in April 2006.
She was accused of the murder of Jane Driver in 2000, Eva Blackburn in 2001 and Annie Midgley in 2002.
She was also charged with the attempted murder of a 42-year-old man and 13 counts of unlawfully administering poison to 12 other patients.
The attempted murder charge related to the death of Michael Parker in 2002.
Amy Newman, the older sister of Eva Blackburn, said the death of Ms Grigg-Booth had robbed her of the chance for answers.
"I didn't know anything about this until about two years ago when the police called," the 84-year-old said.
"I would have just liked to know why she did it. Now I will never find out."
Detectives picked out a number of suspicious deaths at the hospital
Det Supt Phil Sedgewick, who led the investigation, said no one would ever know how many patients the nurse had killed.
He added that the difficulty of proving exactly how her ill and elderly patients had died, especially since many had been cremated, meant the Crown Prosecution Service decided to proceed with just three murder charges.
He said: "We looked at a lot of deaths at the hospital and picked up a number of suspicious cases.
"We eventually concentrated on between 15 and 20 cases and brought experts in to look at these.
"It was eventually decided to go ahead with three murder charges, one attempted murder and the rest as administering poison charges."
When asked if he thought she may have killed more than three, he said: "She could have. We just don't know. Now we'll never know for sure."
A spokeswoman for Airedale General Hospital said staff were sorry to learn of her death and offered their condolences to her family.
An inquiry has now been launched by the West Yorkshire Strategic Health Authority into the circumstances surrounding the deaths.
Ms Grigg-Booth was divorced and had one son.