He had just celebrated his 21st birthday [Image: Scott Garfitt/REX]

Rising rapper Juice Wrld allegedly popped pills on the private jet he flew on and touched down at Chicago Midway airport before he suffered seizures and died.

According to police, people on the plane say the 21-year-old rapper had "popped several pills" prior to suffering seizures.

TMZ report the private jet he flew on was loaded with 70lbs of marijuana.

Law enforcement sources told the publication how FBI had confiscated the "huge stash" of weed from suitcases on board the flight.

And according to the same source, several of Juice's team who were aboard the flight told them he had taken "several unknown pills" prior to the seizures.

Juice Wrld was about to become a rising star [Image: AFF-USA/REX]

The private jet landed at around 1am on Sunday after flying in from California. The publication also reports how one of Juice's associates told authorities the rapper had a Percocet problem.

Law enforcement sources also say a bottle of codeine cough syrup was found on the plane.

However, the star's cause of death hasn't been given - an autopsy will be conducted by the Cook County Medical Examiner on Monday.

READ ALSO: Juice Wrld predicted his own death as he rapped about not making it past 21

Juice Wrld - real name Jarad Anthony Higgins - reportedly became sick at the airport and was rushed to hospital, where he later passed away.

He is said to have been still conscious when he was transported to the medical centre, but died a short time later.