The deaths of two elderly patients in Chicago hospital have prompted a police investigation.
The two died from an insulin overdose and one other remains in a coma and authorities suspect they may have deliberately been given an overdose of insulin.
Officials at the Chicago Medical Center were called in after the three patients appeared to have received unusually high amounts of insulin.
The Chicago Police Department says the investigation is in the early stages and as yet they do not know if there was criminal intent.
The hospital says whether it was a medical error, a question of product integrity or defective test results, is at present unclear.
It appears that all of the patients were elderly women, being treated in the same wing of the hospital; they were not diabetic and had not been prescribed insulin.
The hospital has launched it's own internal investigation and has increased security with regard to its insulin storage.
None of the staff working at the hospital have been reassigned.
The death of another woman who suffered from symptoms consistent with a sharp increase in insulin is also being investigated.