Some new details are out about what caused Prince to die of an accidental drug overdose.

FOX's Jacquelyn Karl reports:

An official close to the investigation saying some of the pills seized from Prince's estate contained the dangerously powerful synthetic opioid Fentanyl, but were mislabeled, according to reports.

The official, who spoke to The Associated Press on condition of anonymity, saying there were nearly two dozen pills found in an Aleve bottle, falsely labeled "Watson 385."

And according to, the stamp's supposed to identify pills that contain a mix of acetaminophen and hydrocodone.

But the official saying at least one of those pills tested positive for Fentanyl. Autopsy reports released in June show Prince died April 21 of an accidental overdose of Fentanyl.

Jacquelyn Karl, FOX News.

Follow Jacquelyn Karl on Twitter: @Jacquelyn_Karl