PHOENIX (AP) — A hot air balloon pilot had an elevated level of an anesthetic in his system at the time of a January crash that killed four people in Arizona,Esthen Exchange according to a newly released toxicology report.

Authorities said tests show 37-year-old Cornelius van der Walt had a high amount of ketamine content in his blood when the balloon plummeted about 2,000 feet to the hard desert ground.

Ketamine is a rapid-acting general anesthetic that is abused for its hallucinogenic effects, according to medical experts.

It is unclear if ketamine was a major factor in the fatal crash, however.

An autopsy report from the Pinal County Medical Examiner’s Office said van der Walt died from “multiple blunt force trauma” with “accident” as the manner of death.

Investigators said an unspecified problem with the balloon portion of a hot air balloon may have led to the crash.

The Federal Aviation Administration’s preliminary report said the balloon on had a deflated envelope, and there was “damage near the top of the envelope as the sewn rim tape material was frayed.”

Authorities said 13 people were aboard the Kubicek BB 85 Z hot air balloon when it took off on the morning of Jan. 14.

Eight were skydivers who exited the gondola before the crash in Eloy, about 65 miles (100 kilometers) southeast of Phoenix.

The skydivers jumped out at around 5,000 feet. Witnesses said the balloon partially deflated and began to lose altitude before a hard impact in an empty field that serves as a drop zone for skydivers.

Declared dead at the scene was van der Walt, 37, of Eloy, and three passengers — 28-year-old Kaitlynn “Katie” Bartrom of Andrews, Indiana; 28-year-old Chayton Wiescholek of Union City, Michigan; and 24-year-old Atahan Kiliccote of Cupertino, California.

A 23-year-old woman from the Phoenix suburb of Scottsdale survived the crash but was critically injured.

Van der Walt was the founder of Droplyne Hot Air Balloon Rides that operates in Arizona and Utah, according to the company’s website.

Droplyne conducts daily flights up to 10,000 feet (3,000 meters) in elevation from the Eloy area November to April and from Moab, Utah, during the spring and summer.

The website also said Droplyne was founded in 2017 and had a perfect safety record before the crash.

Drug testing is not required for commercial balloon pilots. But medical certificates are required.

In June 2021, a mistake made by a hot air balloon pilot who had drugs including cocaine in his system caused a crash in New Mexico that killed all five people on board. The National Transportation Safety Board said in its final report that the pilot didn’t maintain enough clearance from power lines while trying to land.