The family of a man whose death is being linked to contaminated saline at a Stockport hospital say they fear other deaths may be uncovered.
The deaths of George Keep, 84, Arnold Lancaster, 71, and Tracey Arden, 44, at Stepping Hill Hospital are being investigated by police.
Mr Keep's daughter, Carolyn Knowles, said she was "concerned" that the number of suspicious deaths would rise.
Insulin was found in 36 saline ampoules in a storeroom at the hospital.
Greater Manchester Police say the saline was deliberately contaminated.
Mr Keep, from Cheadle, Stockport, had lung cancer and had been admitted to Stepping Hill on 27 June after breaking his hip in a fall.
He died on 14 July two days after a nurse raised concerns about unusually high numbers of patients having unexplained low blood sugar levels.
Results of post-mortem examinations on Mr Keep's body and those of Ms Arden, who suffered from multiple sclerosis, and Mr Lancaster, who died on 11 July, are due to be released later this week.
Detectives believe the contaminated saline was used in drips on at least two wards.
Ms Knowles said her father had been recovering well until two days before his death when his blood pressure and blood sugar levels started to drop.
She said: "If you go into hospital, it is supposed to be a safe place.
"It is a place where you trust people. You just don't... imagine anything like this could possibly happen. I just cannot imagine anyone wanting to do that to someone else.
"It is devastating. I just hope that it is not going to happen to anybody else and other families."
Her husband David said: "If the police start looking into the past, they might find all sorts of awful things and that doesn't bear thinking about."
Greater Manchester Police's major incident team said it was focusing its investigation from 7 July but said it would review previous deaths at the hospital if new information comes to light.
Officers are continuing to interview doctors, nurses, porters, patients and visitors, while security remains high in and around the hospital.
Eleven people who survived the effects of the tampered medication are also going to be interviewed.
Ms Arden's brother Gary said: "During the afternoon my mother and father had been to visit her, then they left her looking like she was recovering well.
"Colour was coming back into her cheeks and so on, she was responding well to her treatment.
"They left and then a relatively short while afterwards they received a call from the hospital that Tracey had taken a turn for the worse and they think they should come on and see her.
"By the time my mother and father arrived, she had just passed away."