Officials are fighting a brush fire that sparked near Buckeye late Sunday. The Arizona Department of Forestry said the fire, called the Robbins Fire, started in the Robbins Butte Game Preserve. It has since burned into the river bottom, officials said. The fire is burning about 48 acres six miles southwest of Buckeye. Heavy smoke is expected Monday due to the vegetation that the fire is burning in. There are multiple engines and two hand crews assigned to the fire. The cause of the fire was not immediately known. It is under investigation.