By Char Adams
Updated August 22, 2016 at 03:36 PM EDT
Kevin Winter/Getty Images

Prescription pain pills found hidden in an Aleve bottle at Prince‘s Paisley Park estate may have been counterfeit drugs that contained the much stronger narcotic fentanyl, according to reports.

At least one of the pills, which were labeled “Watson 385” — indicating that they contained lower-potency mix of acetaminophen and hydrocodone — tested positive for fentanyl, a source close to the investigation told the Associated Press on condition of anonymity.

Fentanyl is 50 times stronger than heroin and up to 100 times more potent than morphine.

The “Purple Rain” singer may have taken the pills not knowing that they contained the more powerful drug and accidentally overdosed, a source told the Minneapolis Star Tribune.

Prince, 57, was found unresponsive in an elevator on April 21, and officials later revealed that the singer died of a fentanyl overdose.

Nearly two dozen prescription narcotic pills were found in a bottle of the over-the-counter medicine Aleve, the source tells the AP.

Records showed that the “Purple Rain” singer had no prescription for any controlled substance in the state in the year before he died, the source told the AP, adding that authorities are working to determine how Prince obtained the drugs.

The Star Tribune first reported the news, with a source telling the newspaper that the pills were marked as hydrocodone.