Heroin tainted with a powerful painkiller called fentanyl is responsible for at least 17 deaths in the Pittsburgh area, authorities said.
The tainted heroin, some sold in bags marked “Theraflu,” has killed at least 17 people, including five suspected overdoses, since Friday.
Fentanyl is about 100 times as powerful as morphine, reported CBS Pittsburgh.
Allegheny County typically sees 250 fatal overdoses a year, according to medical examiner Dr. Karl Williams. At this rate, the county will see 800 overdose deaths in 2014.
Pittsburgh Mayor Bill Peduto issued a warning Sunday asking drug users not to take the drug.
"Those who are in possession of this potent formula are in danger of losing their lives," Peduto said in a statement. "It will kill you. The danger cannot be overstated."
Toxicologists are working to determine how concentrated the fatal doses were.