It is unclear if the found painkillers played a role in the music icon's death.
According to NBC News, the county sheriff has asked for the help of the Drug Enforcement Administration in investigating Prince's death.
The DEA's role will be to determine where the drugs came from, and what prescriptions Prince had obtained.
An autopsy for Prince was conducted last Friday, but it will likely be weeks before results of toxicology tests are delivered.
A cause of death is yet to be determined.
Prince was found unconscious at his home on Thursday, April 21. Prior to his death, the musician underwent a treatment when his private jet made an emergency landing in Moline, Illinois on Friday, April 15.
Doctors reportedly gave him a "save shot," which is commonly given to counteract the effects of an opiate.