ABC News December 9, 2019

Authorities discovered marijuana, codeine on Juice WRLD's plane just before medical emergency: Police

WATCH: FBI seizes drugs, guns from private plane after rapper's sudden death

Chicago rapper Juice WRLD suffered an apparent seizure that led to his death while authorities were searching his plane and luggage for drugs and weapons, police revealed Monday.

Police and federal agents discovered 41 bags of marijuana, six bottles of liquid codeine and three firearms when the 21-year-old and his entourage landed at Chicago's Midway International Airport on Sunday, according to the Chicago Police Department.

The department said federal investigators asked officers to meet the aircraft when it landed Sunday to assist in a search, but declined to say who may have tipped them off. While the search was happening, Juice WRLD, whose birth name is Jarad Anthony Higgins, began convulsing and going into an apparent seizure, police said.

Owen Sweeney/Invision/AP, File
In this May 15, 2019 file photo, Juice WRLD performs in concert during his "Death Race for Love Tour" at The Skyline Stage at The Mann Center for the Performing Arts in Philadelphia.

Narcan, a life-saving drug that reverses the effects of an opioid overdose, was administered and he was rushed to a nearby hospital, where he later died.

The medical examiner's office said Monday afternoon it was too early to determine the cause of death.

(MORE: Rapper Juice WRLD dead after suffering medical emergency at Chicago's Midway Airport)

"The Cook County Medical Examiner’s Office has determined that additional studies are required to establish the cause and manner of death for 21-year-old Jarad A. Higgins," the office said in a statement. "Additional studies include cardiac pathology, neuropathology, toxicology and histology. The cause and manner of death are pending at this time."

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The rapper's single "Lucid Dreams" peaked at No. 2 on the Billboard Hot 100 chart in the summer of 2018, following the release of his debut album, "Goodbye and Good Riddance." Higgins' 2019 album "Death Race for Love" debuted at No. 1 on the Billboard 200 in March.

ABC News' Alex Perez contributed to this report.