(TEUTOPOLIS, Ill.) — Multiple people are dead and evacuations are in place after a semi-truck carrying a toxic substance overturned in rural Illinois Friday night, authorities said.

The incident occurred around 8:40 p.m. local time on U.S. Highway 40 near the village of Teutopolis, authorities said.

A semi-truck carrying ammonia rolled over, causing a “large plume cloud of anhydrous ammonia on the roadway that caused terribly dangerous air conditions in the northeast area,” according to Effingham County Sheriff Paul Kuhns.

Several vehicles were involved in the crash, state police said.

“I am sorry to say that we do have multiple fatalities,” Kuhns said during a press briefing Saturday morning. “And I’m sorry to say I don’t have that exact number for you.”

The accident scene was “large” and “complicated,” he said.

“We’re still dealing with the crash and the emergency caused by the anhydrous ammonia spill,” the sheriff said.

The east side of Teutopolis has been evacuated in the wake of the crash, with the evacuation zone approximately 2 square miles, authorities said. There is no update at this time on when residents will be able to return to their homes.

The ruptured area of the tanker has been patched, which “slowed it down” but did not stop the leak, Teutopolis Fire Protection District Chief Tim McMahon said.

Anhydrous ammonia is a clear, colorless gas that is toxic. Effects of inhalation range from nausea to respiratory tract irritation, depending on the length of exposure, according to the Centers for Disease Control and Prevention.

Drivers are still being kept away from the area amid the cleanup.

The cause of the crash remains under investigation, Acting Lt. Bruce Wagner of the Illinois State Police said.

The NTSB, in coordination with the Illinois State Police and the Effingham County Sheriff’s Department, is sending a team to conduct a safety investigation into Friday’s rollover crash, the agency said Saturday.

Teutopolis is a small village in Effingham County, located about 92 miles southeast of Springfield, the capital of Illinois.

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