FARWELL (July 14, 2009)--Federal agents launched a investigation Tuesday into the cause of a fire that devastated a large High Plains egg production plant.

The fire at the Cal-Maine Foods plant in Farwell on Thursday killed an estimated 800,000 chickens.

A statement issued by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives says an ATF National Response Team from Lubbock arrived at the scene Tuesday.

The statement says the fire destroyed four of the nine laying houses at the complex and killed chickens in a fifth.

Each of the five destroyed buildings covered 24,000 square feet.

Four firefighters suffered heat exhaustion and smoke inhalation while fighting the flames.

The Texas State Fire Marshal's Office and the Parmer County Sheriff's Department also are participating in the investigation.