MONROE, Wis. — Officials say an explosion at an ethanol plant in southern Wisconsin caused structural damage, but did not result in any injuries to employees or first responders.

Green County Emergency Management Director Tanna McKeon says the explosion occurred in a silo at Badger State Ethanol in Monroe shortly before 6 a.m. Tuesday. McKeon says a fire is slowly burning inside the silo and is contained. She says the extent of the damage to the silo will be assessed after the fire is out.

McKeon says the silo, which can hold a maximum 2,200 tons, was 40 percent full of a ground corn product when the explosion occurred.

The cause of the explosion is under investigation. The plant operates around the clock, but no employees were hurt.

Several other agencies are assisting Monroe firefighters at the scene.