Tyson Foods Inc. said Friday that it has reached a nearly $4 million settlement with the U.S. Environmental Protection Agency to resolve refrigeration-system maintenance concerns at plants in four states.

The EPA said in a release the settlement is a result of eight separate incidents between 2006 and 2010 in which anhydrous ammonia was accidentally released at various Tyson plants, which resulted in one fatality, multiple injuries and property damage. The plants were located in Iowa, Kansas, Missouri and Nebraska.

Anhydrous ammonia, considered a poisonous gas, is often used in industrial refrigeration systems, the EPA said.

EPA said it found multiple occasions of noncompliance with the Clean Air Act's chemical accident-prevention provisions. Failure to follow the general industry standards to test or replace safety valves and improperly co-located gas-fired boilers were among the violations the EPA cited.

The agreement requires Tyson to pay a civil penalty of $3.95 million and create a special program for meeting risk management program requirements of the federal Clean Air Act.

“This settlement will protect workers at Tyson facilities throughout Kansas, Iowa, Missouri, and Nebraska that use anhydrous ammonia, and make the communities surrounding these 23 facilities safer,” Ignacia Moreno, assistant attorney general for the Justice Department’s Environment and Natural Resources Division, said in a statement.

The EPA stated that Tyson's 23 listed facilities are subject to the Clean Air Act, because their refrigeration systems contain more than 10,000 pounds of the chemical, and have a combined inventory of more than 1.7 million pounds.

In a separate release from Springdale-based Tyson, company officials said they disagree with many of the EPA's assertions but recognize there was a period when refrigeration improvements fell behind schedule and the company did not meet all required obligations.

“We strive to operate our facilities responsibly, so after learning of EPA’s concerns we immediately made improvements and cooperated with EPA officials throughout the process,” Kevin Igli, Tyson senior vice president and chief environmental, health and safety officer, said in a statement.

In addition to the civil penalty and special program creation, Tyson will also be required to spend at least $300,000 to purchase anhydrous ammonia-related emergency response equipment for fire departments in eight communities where plants are located.

The communities chosen are: Council Bluffs, Iowa, which has two facilities; Perry, Iowa; Dexter, Mo.; Monett, Mo.; Noel, Mo.; Lexington, Neb.; Omaha, Neb.; and Dakota City, Neb.