EVANSVILLE, Ind. — A leak of anhydrous ammonia that sickened 21 people was caused by someone trying to steal the chemical from a farm supplier, authorities said.

Vanderburgh County Sheriff Eric Williams said investigators found damage to the ammonia’s container and tubing and other paraphernalia that suggested a theft.

Anhydrous ammonia is a key component in the production of methamphetamine. Thefts occur regularly at farms and their suppliers.

Williams told the Evansville Courier&Press that co-op officials were aware of the demand for ammonia for drug production and have taken appropriate steps to secure it, including keeping the tank in a fenced-in area.

“But nothing’s perfect,” Williams said, adding he suspected the business would review its procedures. “Obviously, some people got in there.”

The leak occurred about 10 p.m. Friday at Superior Ag Resources Co-op on Evansville’s west side.

Seven people were taken to St. Mary’s Medical Center and 14 were taken to Deaconess Hospital. All were treated and released.

Sean Datzman, who lives near the co-op, said security should be increased.

“If you have a theft like that and somebody makes a mistake like that, it can cost people’s lives, and that’s not a good situation at all,” Datzman said.

“My chest was burning, my eyes, my throat, my nose burns all burned,” Datzman said. “It just makes it really hard to breathe.”

A representative of Superior Ag Resources said the business had no comment.