British police have linked two more deaths at a northwest England hospital to insulin-contaminated saline, as they continue to hold a nurse for questioning.

Greater Manchester Police say the deaths of an 83-year-old man who died Thursday and an 84-year-old woman who passed away July 14 are now part of the investigation. Three other deaths at the Stepping Hill Hospital in Stockport are being investigated, but the deaths remain officially unexplained.

On Wednesday, police arrested 27-year-old nurse Rebecca Leighton on suspicion of murder, but she has not been charged.

The contamination was discovered last week when a higher-than-normal number of patients showed unexplained low blood-sugar levels. A 44-year-old woman and two men, aged 71 and 84 died, and police are investigating to determine if their deaths were caused by the contaminated saline. Another patient remains in critical condition.

Assistant Chief Constable Ian Hopkins says security at the hospital has been increased since the suspicious deaths. He added that since the police were called in, there have been no further incidents of deliberate damage or contamination.