TEUTOPOLIS, Ill. (WCIA) — A deadly crash in Teutopolis on Friday resulted in a toxic plume of anhydrous ammonia leaking from a tanker truck and spreading in the area, prompting an evacuation of half the town.

But what is anhydrous ammonia?

Most farmers know what it is. It’s used to fertilize crops and Teutopolis’ Fire Chief said it’s pretty normal to see around Central Illinois. It is stored as a liquid, but when the tanker crashed, it started leaking and evaporated into a gas.

Chief Tim McMahon said what when firefighters arrived, it didn’t take long to realize they were dealing with serious chemicals. And the wind was blowing from the east, carrying the cloud of ammonia down Route 40 and toward Teutopolis.

The effects of anhydrous ammonia on the body is quick and potentially deadly, McMahon said.

“It affects your respiratory system, gets into your lungs,” McMahon said. “If you’re in the plume it’s very, very deadly.”

He’s not sure how long it will take to clean up the leak, but evacuation orders will be in place into Sunday morning. Nearly half of the ammonia leaked out of the trailer and responders are trying to find a way to safely transfer the remainder into another tanker.