Cocaine is often diluted — “cut” — with a variety of substances including the deadly synthetic opioid fentanyl. That’s where the bodies of unsuspecting users are piling up.

A federal agency is warning consumers about using illegal online pharmacies after an increase in sales of counterfeit pills made with fentanyl and methamphetamine. The warning comes after the death of one person who bought what she thought was oxycodone but died of fentanyl poisoning.

Illegal online pharmacies are increasingly selling counterfeit pills laced with fentanyl and methamphetamine to customers thinking they’re purchasing prescription drugs from legitimate sources, warned the U.