ATLANTA — Potentially lethal carbon monoxide levels at an Atlanta elementary school with no detectors sent at least 42 students and seven adults to hospitals Monday and forced 500 more to leave school, authorities said.

Young children with oxygen masks over their faces were strapped to gurneys and others carried to ambulances by emergency officials at Finch Elementary School in southwest Atlanta. Four children reported passing out at the school, according to hospital officials. A teacher and a cafeteria worker were also among those treated.