An autopsy performed on Chicago rapper Juice WRLD was unable to determine his cause and manner of death, according to the Cook County medical examiner’s office.

The office, which performed the autopsy Monday, said additional studies were required, including “cardiac pathology, neuropathology, toxicology and histology.”

Results from toxicological examinations can take several weeks to come back.

Juice WRLD, born Jarad Anthony Higgins, died early Sunday at Christ Medical Center in Oak Lawn after suffering cardiac arrest at Midway Airport. He turned 21 last week.

The Chicago Police Department said officers were called to the airport at 1:34 a.m. Sunday to assist federal law enforcement with “a private jet arriving at the airport which contained a large amount of narcotics.”

When police arrived, they found the plane’s passengers in the airport with several pieces of luggage. A drug-sniffing dog from the Illinois State Police indicated narcotics were inside, and officers soon found 41 bags believed to contain marijuana and six bottles of suspected liquid codeine. TMZ reported Monday that authorities seized 70 pounds of marijuana.

Three guns were also found on board, according to police, and two of the plane’s passengers — working as security for the rapper — have since been charged.

Christopher Long, 36, of Buena Park, California, is charged with a misdemeanor count of possession of a firearm, CPD spokesman Anthony Guglielmi said. Henry Dean, 27, of Chatham, is charged with two counts of possession of a firearm and one count of possessing a high capacity magazine, Guglielmi said. They are due in court Dec. 30.

According to the CPD, Juice WRLD suffered a seizure during the search, and a Homeland Security officer administered a shot of Narcan, which is often used to reverse the effects of opioid overdoses.

A representative for the Department of Homeland Security did not respond to a request for comment.

Donielle Davenport, who was Higgins’ chemistry teacher at Homewood-Flossmoor High School in 2015, said she was “heartbroken” to hear of his death.

She said that he was a “compassionate, intellectual leader” who cared about his other classmates and teachers.

“He didn’t always like school, so as an incentive, I’d let him share his music with the class once his work was done,” Davenport said. “It was always mind-blowing to see how talented he was at such a young age. It takes some people a lifetime to find their purpose, but he knew his.”

Davenport said she remembers her former student for his sense of humor. She said she was pregnant at the time she was his teacher, and he would joke that her snacks were bad for the baby so that he could eat them.

Higgins always made the class laugh by “roasting his other classmates.”

“It was all love. I was so proud to see his success on such a large-scale,” Davenport said. “I always hoped I’d get to see him again, but I’ll always remember him for being such a great person.”