Amarillo Fire Department officials say other people who were in the home are "not out of the woods" yet.
Fire officials say a chemical reaction occurred when one person tried to wash off a pesticide that had been sprayed under the house.
Poisonous Phosphine gas was released. Capt Larry Davis said in a statement yesterday that crews responded to a medical call at the home about 5am.
One child died at the scene and three others died at a hospital. Officials didn't release any identifying information, including the children's ages.
Other family members and first responders are being treated.