Authorities are still investigating how Prince obtained the pills.

Pills containing an opioid “50 times more powerful than heroin” have been found in Prince‘s home, according to an official involved in the investigation into his death. Over 20 counterfeit pills thought to contain the powerful tranquilizer fentanyl were discovered in a falsely labelled bottle, the Associated Press report, with another aspirin bottle seized from Paisley Park alleged to have been found containing a further 60 counterfeit tablets.

In June, autopsy results confirmed that the artist died of an accidental fentanyl overdose. Tests carried out on Prince prior to his death however did not detect any fentanyl in his system, indicating that he was not a long-term user of the drug. The pills seized from Paisley Park were reportedly labelled as hydrocodone, a weaker type of opioid.

Some of the dozens of pills found at Prince’s Paisley Park home, the report continues, contained a mix of drugs, including fentanyl, lidocaine and U-4770 – a synthetic drug eight times more powerful than morphine. The pills were in bottles falsely labelled as “Watson 385”, a stamp used to identify pills containing a mix of acetaminophen and hydrocone.

Prince was reportedly found in possession of such pills a week before his death, when his airplane made an emergency stop in Illinois after the star reportedly suffered a mid-flight seizure. Officials say Prince had no prescriptions for controlled substances in the state of Minnesota at the time of his death. Authorities are still investigating how Prince obtained the pills.

Read next: The 10 best Prince songs you never knew existed



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