Five people were killed in a multi-vehicle crash that included a tanker truck carrying a toxic chemical that spilled Friday night, triggering a large evacuation near downstate Effingham.

The truck was holding 7,500 gallons of anhydrous ammonia, of which about 4,000 gallons spilled, according to the Illinois Environmental Protection Agency. The crash happened about 9:25 p.m. Friday in Teutopolis, about 200 miles south of Chicago.

Effingham County Coroner Kim Rhodes said the five dead included three from the same family — one adult and two children under 12. The other two were adult motorists from out of state, Rhodes said. Additionally, five people were airlifted to hospitals, their conditions unknown.

About 500 people were being evacuated from the area of the crash due to the spill. Evacuations were expected to continue through Sunday morning, the IEPA said.

Multiple other injuries were reported, but the number of people and other vehicles involved in the accident weren’t released.

Anhydrous ammonia is a flammable, “colorless, highly irritating gas with a pungent, suffocating odor,” according to the U.S. Centers for Disease Control and Prevention. It’s used by farmers to add nitrogen fertilizer to soil, and also as a refrigerant in the cooling systems of large buildings.

The accident caused “a large plume, cloud of anhydrous ammonia on the roadway that caused terribly dangerous air conditions in the northeast area of Teutopolis,” Effingham County Sheriff Paul Kuhns said. “Because of these conditions, the emergency responders had to wait. They had to mitigate the conditions before they could really get to work on it, and it was a fairly large area.”

Although not strong, crews working overnight struggled against shifting wind.

“The wind changed three or four different times on us,” said Tim McMahon, chief of the Teutopolis Fire Protection District. “That’s another reason we got crews out in different places, reporting back on which way the wind’s going.”

The leak had been partially patched by midday Saturday, and a contractor for the tanker truck, along with state and federal officials, were determining the “best plan to safely empty the tanker,” the IEPA said.

Route 40 between Effingham and Montrose remained closed.

The cause of the accident had not been determined.

Contributing: Associated Press