Investigators say someone left a plate warmer on and it caused a fire at the east side Hacienda restaurant early Monday morning. Evansville firefighters responded to the blaze around 3:30. When they got there, they found the hot plate warmer had ignited grease near the cooking units. Firefighters say the fire was contained to that general area, but there was smoke damage throughout the building. Crews used large fans to ventilate the building and remove the smoke.