Final autopsy reports confirmed that five people who died in a central Illinois tanker crash last month died from exposure to caustic anhydrous ammonia.

Findings from Effingham County Coroner Kim Rhodes' autopsy reports confirmed the five victims, two of whom were children, died from respiratory failure from inhalation and exposure to the gas. Rhodes said in a press release they sustained severe chemical burns to their bodies, eyes and respiratory systems.

Rhodes identified the victims as Danny Smith, 67; Vasile Cricovan, 31; Kenneth Bryan, 34; Walker Bryan, 10; and Rosie Bryan, 7.

Seven people were hospitalized with severe burns from the crash, according to the news release. Two people remain hospitalized in critical condition.

"Numerous vehicles were abandoned at the scene as the individuals fled the crash site on foot," she said in the report. "Traffic on I-70 was shut down due to a crash in the construction zone which resulted in these drivers being re-routed onto Rt. 40."

What happened in the crash?

The multivehicle crash happened on Sept. 29 around 8:40 a.m. on Highway 40 in Teutopolis, about 93 miles southeast of Springfield, and involved a semi-truck carrying 7,500 gallons of anhydrous ammonia, the Illinois Environmental Protection Agency said in a Sept. 30 news release.

Rhodes said in the release the Illinois State Police and National Transportation Safety Board are still investigating the crash.

Illinois State Police Public Information Officer Trooper Rodger Goines didn't immediately respond to USA TODAY's request for comment on Tuesday.

According to a National Transportation Safety Board press conference shortly after the crash, a car tried to pass the semi-truck, causing the truck to jackknife, overturn and land on a trailer hitch near the road, puncturing a hole in the tanker.

The crash prompted police and environmental officials to evacuate around 500 residents within a 1-mile radius of the crash as a plume of the gas escaped.

What is anhydrous ammonia?

Anhydrous ammonia is a gas that's commonly used in the agriculture industry and sometimes in refrigeration.

It is stored as a liquid under pressure and becomes a toxic gas when released, according to the Mississippi State Department of Health.

The compound can be a health hazard if safe handling procedures are not followed. Effects of inhaling anhydrous ammonia range from lung irritation to severe respiratory injuries, with possible death if a person is exposed to higher concentrations. Anhydrous ammonia is also corrosive and can burn the skin and eyes.

"It's terrible, it's bad stuff if you are involved with it and breathe it, especially," Effingham County Sheriff Paul Kuhns, who oversees law enforcement for Teutopolis, said at a Sept. 30 press conference.

If people come in contact with it, the Centers for Disease Control and Prevention recommends immediately removing them from the source and calling a poison control center or seeking medical care.

In 2019, dozens of people were sickened in suburban Chicago after the valves were left open on tanks of anhydrous ammonia on the way to an Illinois farm from a farm in Wisconsin, creating a toxic gas cloud.

In 2002, a train derailment released anhydrous ammonia in Minot, North Dakota, killing one man and injuring hundreds of others, causing burns and breathing problems.

Contributing: Claire Thornton, USA TODAY; Associated Press