Duke Gadd‘s cause of death has been released … the drummer died of an overdose of fentanyl and cocaine — mirroring what Corey Feldman originally said after he passed.

According to a spokesperson for Clark County, Nevada … Gadd died from “combined toxic effects of fentanyl and cocaine.” He also suffered from high blood pressure.

Remember … Corey announced the death on social media — saying Duke died in Las Vegas and sharing a short clip of the musician banging away on the drums.

At the time, Corey said it was a fentanyl overdose … but, Gadd’s family fired off at the star — with his mom, Carol Gadd, saying they hadn’t received final word from the coroner yet and sarcastically calling Feldman “Dr. Corey.”

Initially, Carol said they’d heard Corey had a heart attack — and a drug was probably involved, but no one specifically said fentanyl.

Worth noting … Corey ultimately took down the Instagram post about Duke — so, it seems he realized he waded into territory he probably shouldn’t have.

Duke was the son of legendary drummer Steve Gadd. He was 41.