A toxic chemical spill snaking its way toward Lake Erie forced the evacuation of hundreds of people and fouled drinking water for at least 22,000 along the Sandusky River in Ohio. At least three people were treated for injuries after an estimated 100,000 gallons of toluene, a flammable chemical that can produce irritating or poisonous gases, spilled Wednesday into the river from a ruptured Sun Co. pipeline near Fremont. That city stopped pumping water from the river after it was estimated that a 14-mile section was contaminated, officials said. They fear the spill killed up to 1,000 fish, and could affect waterfowl. Gov. Richard F. Celeste declared a state of emergency for Sandusky County. About 4 million gallons of water, one day's normal supply, was put in reserve tanks before the spill arrived, said an official at Fremont's water plant.