Law enforcement officials were waiting for the plane when it landed, having received information that banned substances might be onboard.

It was during a subsequent search of the aircraft that the rapper had a seizure that led to his death.

An autopsy on the 21-year-old has proved inconclusive.

The Cook County Medical Examiner's Office said on Monday that additional studies were needed before they could determine the cause of death.

Police in Chicago said they did not suspect foul play; but gave some additional details that shed light on the sudden death of one of hip-hop's brightest rising stars.

Their search uncovered 41 "vacuum-sealed" bags of marijuana, six bottles of prescription codeine cough syrup, two 9 mm pistols, a .40-caliber pistol, a high-capacity ammunition magazine and metal-piercing bullets, authorities told the US media, including the Chicago Tribune and the New York Times.

Two men identified by police as Juice Wrld's security guards have been charged with illegally possessing guns and ammunition.

'Rest ya soul'

Anthony Guglielmi, a Chicago police spokesman, said the star "began convulsing (and) going into a seizure" as authorities were searching two carts of luggage at about 2am on Sunday morning.

Federal agents quickly administered Narcan, a drug used to revive people thought to be overdosing on opioids, and the Chicago Fire Department was on the scene in under seven minutes, Guglielmi said.

Higgins woke up but was incoherent and, after being taken to hospital, was pronounced dead just after 3am.