While police have said they don't believe foul play or suicide is suspected in the death of Prince, reports suggest that local law enforcement in Minnesota have turned the investigation into a criminal probe.

According to Minnesota Star-Tribune, the Carver County Sheriff’s Office have cited an exception to Minnesota’s public-record laws, allowing police to release very little information related to a "criminal" probe about the 911 call placed from inside the Paisley Park complex where Prince was found dead on April 21.

Sources with "direct knowledge of the case" told the Star Tribune that police are investigating the possibility that an overdose of opioids led to Prince’s death. Prescription pills were found at Paisley Park, but it wasn't clear if they belonged to Prince. Investigators are reportedly trying to determine how Prince got the pills.

Between 2013 and his death, four medical emergency calls were made from within his home, according to CNN. Police responded to 911 calls for medical assistance on October 23, 2013; August 9, 2015; September 6, 2015; and, tragically, on April 21, 2016.

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