Authorities investigating the death of music legend Prince found prescription opioid medication on his person and in his Minnesota home, a law enforcement official told CNN on Wednesday.

The pills are commonly used to treat pain, and investigators have brought in the U.S. Drug Enforcement Administration to help with the case, the source said.

Investigators believe a health scare about a week before Prince’s death, which caused an unscheduled landing of his plane in Illinois, was likely the result of a reaction to the pain medication, the official said.

The pilot told air traffic control that a passenger, later known to be Prince, was unresponsive.

Prince was treated for a potential overdose of pain medication, the official said.

The singer was reportedly rushed to a hospital in Moline. His publicist, Yvette Noel-Schure, later said he returned home and was fine.

Prince was 57 when he died last week at his home in a Minneapolis suburb.

Autopsy done

Investigators are still awaiting results of autopsy and toxicology tests for further understanding of why Prince died.

The Midwest Medical Examiner’s Office in Ramsey, Minnesota, performed the autopsy on the much-loved musician on Friday. Dr. A. Quinn Strobl finished the procedure in four hours, according to the office, but Strobl won’t declare what caused Prince’s death until after the office gathers all the relevant details. That will take weeks.

Prince was found unresponsive in an elevator at Paisley Park, his home and studio in Chanhassen, Minnesota, on Thursday. Paramedics performed CPR but were unable to revive him.

Carver County Sheriff Jim Olson said there were no obvious signs of trauma on Prince’s body when he was found.

The last time Prince was seen alive was at 8 p.m. Wednesday when he was dropped off at Paisley Park, the sheriff said. He was alone in the complex when he was found, which Olson said was not unusual given Prince’s private persona.