Rapper Juice WRLD was treated for opioids on his private jet before his death, police officials have confirmed.

The 21-year-old rapper was on a plane with around 12 other people when it landed at Midway International Airport on Sunday. According to Chicago police spokesperson Anthony Guglielmi, federal agents and city police officers were waiting for the aircraft when it landed, after being tipped off that a private plane travelling from Los Angeles to Midway was carrying guns and drugs.

During the search of luggage carts loaded with bags from the plane, a sniffer dog made a "positive alert", at which point officers found numerous bags of suspected marijuana, bottles of prescription cough syrup, three guns, metal-piercing bullets and a "high-capacity ammunition magazine".

It was during the search that the rapper, real name Jarad Higgins, started going into convulsions. After his girlfriend said he'd been taking Percocet, an opioid painkiller, one of the agents administered Narcan in a bid to revive the star.

According to the Chicago Tribune, the musician woke up briefly but was incoherent. He was later pronounced dead at the nearby Advocate Christ Medical Center in Oak Lawn at around 3.15 am on Sunday morning.

Police have yet to confirm or deny reports that the rapper swallowed a host of Percocet tablets in a bid to hide them from officers and agents conducting the search. According to TMZ, the swallowing of the tablets may have led Juice to overdose - thereby leading to his death.

An autopsy on the rapper's body was completed on Monday, but additional testing was ordered. The results have yet to be announced.