CLARKS GROVE, Minn. (AP) - Authorities are investigating after 9,000 gallons of a dangerous gas leaked at a fertilizer plant in southern Minnesota.

The Freeborn County Sheriff's Office says about 15 homes were evacuated Monday for a couple of hours after anhydrous ammonia leaked at Watonwan Farm Service's Clarks Grover Fertilizer. The colorless, pungent gas is highly irritating and can burn the eyes, nose and throat in even small amounts.

The chemical is a common farm fertilizer. A company spokesman says no employee injuries have been reported. He says first responders were instrumental in containing the leak.

A firefighter was treated at the scene for inhalation issues suffered during the evacuation.

Clarks Grove is a town of about 700 people about 5 miles north of Albert Lea.