WOODSTOCK, Ontario (AP) — Police say a nurse has been charged with the murders of eight elderly people at nursing homes in southwestern Ontario over seven years.

Woodstock Police Chief William Renton said Tuesday that 49-year-old Elizabeth Tracey Mae Wettlaufer was charged with first-degree murder in the killings that took place between 2007 and 2014.

Renton says the victims ranged in age from 75 to 96.

Police say the victims were administered a drug, but declined to identify which one.

Caressant Care Nursing and Retirement Homes, a private nursing home chain, has said one of its former employees is the focus of the investigation.

Caressant, which operates 15 Ontario facilities located mostly in small towns, says the former employee is a registered nurse who left the company 2 1/2 years ago.