The Sept. 29, 2023, crash left five people dead and caused several injuries, according to Illinois officials. (News Nation / WTWO / AP)

(CNN) — An Illinois father and his two young children are among the five people killed by anhydrous ammonia exposure after a semi-truck carrying thousands of gallons of the toxic substance crashed Friday, the local medical examiner’s office announced.

Those killed in the incident have been identified as Kenneth Bryan, 34, and his two children – Rosie, 7, and Walker, 10 – along with Danny J. Smith, 67, and Vasile Cricovan, 31, the Effingham County Coroner’s Office said in a release.

A preliminary examination indicates all five died from exposure to the leaked ammonia and official autopsies will begin Monday, the office said.

A 15-person National Transportation Safety Board (NTSB) team including motor carrier, hazmat and survival factors investigators arrived at the Effingham County site on Sunday, according to NTSB spokesperson Jennifer Gabris.

The sequence of events that led to the accident appears to have started when someone tried to pass the truck, the NTSB said at a Sunday media briefing.

“Preliminary information indicates that another vehicle may have been involved in a passing maneuver near the tanker truck. The driver of the truck appears to have reacted by pulling to the right,” said board member Tom Chapman. “The tanker truck departed the roadway. After departing the roadway, the truck rolled over, and the cargo tank was compromised.”

The truck was carrying about 7,500 gallons of anhydrous ammonia at the time of the Friday evening wreck, according to the Illinois Environmental Protection Agency. The agency said early estimates indicate more than half of that – about 4,000 gallons – was released.

Several people were hospitalized due to ammonia exposure after the crash, including five who needed to be airlifted to local medical facilities, the coroner’s office said.

The accident happened on US Highway 40 near Teutopolis, Illinois, about 100 miles northeast of St. Louis. The NTSB is investigating whether the tanker truck was rerouted onto the smaller highway due to an earlier crash on Interstate 70.

“As it rolled over, the tanker truck jackknifed and exposed the head end of the tank,” said Chapman. “As momentum carried the tank forward, it came into contact with the hitch on the utility trailer. The hitch punctured the cargo tank, leaving a hole approximately 6 inches in diameter.”

Approximately 500 people within a 1-mile radius of the crash were evacuated from parts of Teutopolis following the crash but were allowed to return to their homes Saturday night.

“Testing has indicated that the danger from the anhydrous ammonia has dissipated,” Teutopolis Assistant Fire Chief Joe Holomy said in a Saturday night news release. “We have notified residents that they may return home.”

Crews worked overnight Friday into Saturday to patch part of the rupture on the semi-truck – which slowed down the leak but did not stop it completely, according to Teutopolis Fire Chief Tim McMahon.

The crashed tanker has since been drained, patched, and taken to a secure location to be investigated by the NTSB, the state emergency management agency said in a news release. The Illinois State Police is also investigating the cause of the accident, it said.

What is anhydrous ammonia?

Anhydrous ammonia “is essentially pure (over 99 percent) ammonia,” says the Occupational Safety and Health Administration (OSHA). “‘Anhydrous’ is a Greek word meaning ‘without water;’ therefore, anhydrous ammonia in ammonia without water.”

Ammonia used in households is a diluted water solution that contains 5 to 10 percent ammonia, according to OSHA.

Ammonia in high levels can irritate and burn the skin, mouth, throat, lungs and eyes, according to the Centers for Disease Control and Prevention. Very high levels can also damage the lungs or cause death.

Symptoms of anhydrous ammonia exposure include breathing difficulty; irritation of the eyes, nose or throat; and burns or blisters.

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