Lil Peep’s death has sparked an investigation.

Law enforcement officials are now trying to see whether fentanyl, a powerful and potentially deadly opioid, led to the 21-year-old rapper’s untimely passing, according to TMZ.

Tucson officials have reportedly received multiple tips about the New York rapper’s death and some believe that he was given drugs laced with the opioid, which has also contributed to accidental overdoses of Prince and others. The drug is usually used to treat ongoing severe pain.

Peep’s cause of death remains unverified. He was allegedly found dead on a tour bus with drug paraphernalia, Xanax, marijuana, and an unknown powder on Nov. 15. He was 21.

The rapper’s older brother Karl “Oskar” Åhr told PEOPLE that Peep may have taken a pill that was laced. “We [the family] have heard there was some sort of substance he did not expect to be involved in the substance he was taking,” he said. “He thought he could take what he did, but he had been given something and he didn’t realize what it was.”

Oskar went on to say that he believed Peep did not want to kill himself. “It was an accident, it really was an accident,” he said. “He was super happy with where he was in life.”