Special "resources and expertise" have been called in to the investigation of Prince's death.

The legendary music icon was found dead in an elevator at his Paisley Park estate in Chanhassen, Minnesota, on April 21. Now, as reports surface of alleged drug abuse, the DEA and US Attorney's Office have joined the local sheriff's department to determine the cause of death.

"The US Attorney's Office and DEA are joining the Carver County Sheriff's investigation. The DEA and US Attorney's Office are able to augment this local investigation with federal resources and expertise about prescription drug diversion," a spokesperson for the US Attorney's Office told ET. "While this remains an ongoing investigation, we will have no further comment."

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A law enforcement source previously told CBS News that prescription drugs were found in Prince's possession at the time of the singer's death and that the DEA had been contacted.

It was reported on Wednesday that Dr. Howard Kornfeld, who runs Recovery Without Walls in Mills Valley, California, and deals with opioid addiction treatment, was called by Prince's reps on April 20 because the "Purple Rain" singer was "dealing with a grave medical emergency."

"He was in pain all the time, but he was a performer," Prince's friend and longtime collaborator, Sheila E. exclusively told ET, citing injuries the musician sustained from jumping off risers during concerts.

Find out what else she had to say in the video below.