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Earlier this month, Lil Peep died of a suspected drug overdose in Tucson, Arizona. The final toxicology results will not be determined for another four to six weeks, but police are reportedly investigating the involvement of fentanyl, the deadly opioid which has become a growing concern in Arizona and beyond, as SPIN points out.

TMZ has reportedly been told by law enforcement sources that police are investigating it as a possible cause:

Cops in Tucson are on the hunt after receiving multiple tips the New York rapper got his hands on some incredibly toxic drugs laced with the potent opioid.

Fentanyl is typically laced into other drugs without its user’s knowledge, and also contributed to the accidental overdose of Prince last year. And as the Arizona Daily Star writes, “nearly 140 pounds were seized this year at Arizona’s ports, enough deadly doses for almost 32 million adults, and enough to make traffickers up to $1.3 billion.” A tiny dose of it can be fatal, and it’s “50 to 100 times more potent than morphine.”

We will update as more information is revealed.