British police are investigating whether three hospital patients died as a result of receiving saline solution contaminated with insulin.
Detectives were hunting Saturday for the person who tampered with a batch of saline at Stepping Hill Hospital in Stockport, northwest England.
The contamination was discovered earlier this week after a nurse reported a higher-than-normal number of patients with unexplained low blood sugar levels.
Detectives are awaiting post-mortem results to determine whether three patients _ a 44-year-old woman and two men aged 71 and 84 _ died as a result of the contamination.
Eleven other patients who received the contaminated saline were mildly affected and will be interviewed by police, along with all the hospital's medical staff.
"(The investigation) is at a very early stage and we don't know what effect, if any, the solution has had to the well-being of any patients," said Assistant Chief Constable Terry Sweeney.
"That said, we have someone deliberately contaminating saline in the one place that people should feel they are being most cared for," he said. "I want to reassure everyone connected to the hospital _ staff, patients, visitors and the wider community _ that we are determined to prevent further harm and to bring the offender to justice. "
Hospital officials said they had increased security at the facility, 150 miles (250 kilometers) northwest of London.