Prince performing at the Zenith in Paris, 1986 Getty Images

The federal Drug Enforcement Administration has joined the investigation into the death of Prince after prescription pain pills were found on the singer's body and in his Paisley Park home. Officials refused to reveal specifically what kind of pills were found — only that they were opioids, a highly addictive class of drugs.

Michael Padden, a longtime attorney for two of Prince's siblings, now deceased, said the singer's late brother and sister told him that Prince abused the painkiller Percocet — as well as cocaine, reports the Minneapolis Star-Tribune.

They "both were really concerned it would end his life prematurely," Padden told the newspaper. A man claiming to be Prince's drug dealer has also said that the singer was hooked on Dilaudid pills and Fentanyl patches — both opioids — and that he was unable to perform sober.

Investigators are attempting to determine what role the painkillers found on his body may have played in Prince's death. While the pills recovered were prescription drugs, officials were not clear if the prescriptions were written for Prince. Padden said that Prince often paid people to obtain prescriptions for him but they were made out in their names.

TMZ recently reported that the iconic musician had suffered a drug overdose just days before his death and was rushed to an Illinois hospital after an emergency runway touchdown as he was flying home to suburban Minneapolis from a concert in Atlanta. He was reportedly given a "save shot" of Narcan to bring him out of an opioid OD. Officials now believe that whatever caused the OD was likely linked to the pills found on the death scene, according to CNN.

The Star Tribune is reporting that Prince was carried from his plane unconscious in the middle of the night during that emergency stop. Local paramedics, responding to a call of an "unresponsive passenger" on Prince's flight, worked to revive the musician before speeding him to hospital, according to fire and ambulance records released by the city of Moline, Illinois.

An audio recording of the pilot requesting an emergency landing reports an "unresponsive" passenger.

Neither foul play nor suicide is suspected in Prince's death. It could be weeks before a cause of death is determined as officials await toxicology results from Prince's autopsy.