Some of the pills taken from Prince's estate after his death were labeled as hydrocodone when they actually contained fentanyl, a synthetic opioid that is 50 times more potent than heroin, according to sources close to the investigation. The source said about two dozen pills were found in an Aleve bottle at Prince's Paisley Park estate and were falsely labeled as "Watson 385." Autopsy results have concluded the Minnesota-based musician died on April 21 of an accidental fentanyl overdose. The source said Prince weighed only 51 kilograms when he died and had so much fentanyl in his system it would have killed anyone. Prince did not have a prescription for fentanyl, the source said. The Star Tribune in Minneapolis first reported the story late Saturday. Investigators still are not sure how the 57-year-old superstar ingested the drug, but they are speculating he took the pills without knowing they contained fentanyl. Although the probe is far from over, investigators are inching closer to the conclusion that Prince was a casualty of what some believe is a national crisis involving counterfeit pills.