Prince was found with prescription painkillers in his possession when he died, according to a new report.
NBC reports that the county sheriff investigating his death is now asking the Drug Enforcement Administration to help with the investigation.
Federal law enforcement officials who spoke to NBC did not reveal what part the medications may have played in Prince's death. Officials say the DEA will help determine the origin of the medication and what prescriptions the singer had obtained.
For more on Prince's private world and tragic death, pick up this week's issue of PEOPLE, on newsstands Friday.
Sources confirm to PEOPLE in this week's cover story that Prince once had a history of using the prescription painkiller Percocet.
An autopsy of Prince's body was conducted just one day after he was found unresponsive in an elevator at his famed Paisley Park estate outside Minneapolis. While the medical examiner found "no obvious signs of trauma," toxicology reports may take weeks to complete.
Other sources tell PEOPLE that the "Raspberry Beret" singer had also been struggling with an "ongoing illness" at the time of his shocking death – just under one week after his private plane made an emergency landing in Moline, Illinois so that he could be rushed – unresponsive – to the hospital to receive what several reports called a "save shot."
Meanwhile an addiction expert tells PEOPLE that prescription painkiller Percocet can be addictive and deadly.
"Overdose and death is a risk that everybody has when we use opiates," Peter Grinspoon, M.D., a Massachusetts-based primary care physician and recovering addict who is nine years sober, tells PEOPLE.
Drugs like Percocet – which is a combination of acetaminophen and oxycodone – are addicting because they can cause "severe euphoria" by stimulating specific "opiate" receptors in the brain, says Grinspoon, 50, who wrote about his opioid addiction and recovery in his memoir Free Refills.