Hospitals in the United States and Canada are reporting cases of people overdosing after using cocaine laced with fentanyl, HealthDay reports.

In Fresno, California, four people were brought to local emergency rooms after using cocaine containing fentanyl. Two of the people died. In Chico, California, one person died and 14 more were hospitalized and later released after using fentanyl-laced cocaine. In all cases, people said they thought they were snorting cocaine, the Centers for Disease Control and Prevention (CDC) reported.

There have been other reports of outbreaks caused by fentanyl disguised as cocaine in New Haven, Philadelphia, and British Columbia, Canada, the CDC said.