Investigators searched for the cause of a chlorine spill that sent dozens of people to the hospital and forced thousands of others to flee their homes.

Gov. Bob Miller said state officials would make sure the Pioneer Chlor Alkali Co. plant was safe before allowing it to open again following a tour of the facility Monday afternoon.A 1-inch crack in a pipeline at the facility spawned a cloud that hung over the city early Monday, prompting authorities to order much of the Las Vegas suburb evacuated until the crowd dissipated because of wind and warmer temperatures.