EXCLUSIVE

Prince was treated for a drug overdose 6 days before his death ... multiple sources tell TMZ.

We broke the story ... Prince's private jet made an emergency landing in Moline, Illinois last Friday, hours after he performed in Atlanta. At the time his reps said he was battling the flu ... something we questioned because his plane was only 48 minutes from home before the unscheduled landing.

Multiple sources in Moline tell us, Prince was rushed to a hospital and doctors gave him a "save shot" ... typically administered to counteract the effects of an opiate.

Our sources further say doctors advised Prince to stay in the hospital for 24 hours. His people demanded a private room, and when they were told that wasn't possible ... Prince and co. decided to bail. The singer was released 3 hours after arriving and flew home.

We're told when Prince left he "was not doing well."

We know authorities in Minnesota are trying to get the hospital records from Moline to help determine cause of death.