Four people were hurt in an explosion in Webster City today around 10 a-m in the feed mixing area of the United Co-op.Webster City fire chief Mike Lund says a cutting torch being used to replace a heating element in an animal fat container apparently ignited fumes. A block near the area was evacuated for a time this morning. Three of the victims are reported in good condition and one is in serious condition. Firemen were also called back when a small fire was discovered in a nearby feedbag storage area. That fire was put out quickly.