An anonymous source claims Prince was suffering from a long-term illness prior to his death at his home in Chanhassen, Minnesota, on April 21.
The comments, which have not been confirmed as true, were made to People Magazine as investigations continue into the cause of the musician’s death.
“The people close to him were very concerned for his health and indicated he'd been undergoing treatments which made his immune system weak,” the source said, according to People.
Carver County Sheriff Jim Olson stated on April 22 that there was no sign of trauma on the singer’s body. He added Prince likely died alone.
“We have no reason to believe at this point that this was a suicide,” Olson added, according to BBC. “But again, this is early on in the investigation and we’re continuing to investigate."
Prince kept his personal life private during his career, and nothing was publicly known about any illness he may have had.
An autopsy was performed on April 22. Martha Weaver, a spokeswoman for the medical examiner’s office, said full tests, including tissue and blood samples, would be carried out before any details were released.
“The thing that really bothers me about it is the Prince I know was super-healthy, vegan, wasn't an abuser of drugs, wasn't an abuser of alcohol,” said collaborator and friend L.A. Reid, according to People. “He was clean and he looked young and he looked really healthy and vibrant so the whole thing is really mysterious to me.”
Friends suggested he had hip problems caused by jumping off risers and speakers on stage while wearing high heels.
“There was always something kind of bothering him, as it does all of us,” Sheila E, Prince’s former percussionist, said, according to BBC. "I hurt every single day. We're like athletes, we train, and we get hurt all the time. We have so many injuries.”
Prince sold more than 100 million records during his career, which began when he released his first album in 1978. His most recent record, HITnRUN Phase Two, was released in 2015.
Fans have set up memorials in his home town of Minneapolis, Minnesota, and in New York.
U.S. President Barack Obama, who is currently visiting Britain, said he started his day April 22 by listening to Prince’s hit “Purple Rain” before beginning his engagements.
Prince’s body was released to his family April 22 following the autoposy.