Three men sustained serious burns in an apparent explosion Tuesday at the Delaware City Refinery. A "minor explosion" occurred about 11:30 a.m. Tuesday during equipment maintenance, according to the state fire marshal. The men were taken to Christiana Hospital and later transferred to the burn unit in Crozer Medical Center in Upland, Pa. A spokeswoman for the Delaware City Refining Company said the men were contractors. The refinery disputes that there was an explosion, but did not explain how men were injured. A 39-year-old worker was burned on his face and arms and was admitted in critical condition, New Castle County Paramedics said.