Evacuation orders remained in place for about 50,000 people in Garden Grove, California, located south of Los Angeles.
A small fire on a Rose Parade float that caused a delay in the parade on New Year's Day may have been started by transmission fluid, according to officials.
Officials said the problem was the chemical glycol leaking from the heating and air conditioning unit at Gantner Elementary School. Illnesses were reported on both Wednesday and Thursday, but the building has since been ruled safe.
Officials cleared the Gantner Avenue School in Elmwood Park to reopen after an indoor air quality test over the weekend came back clean.
An elementary school in New Jersey is closed Friday after a chemical leak sickened several students and some employees, and administrators are working to resolve the situation by the start of the next school week.
It happened at Gantner Avenue School in Elmwood Park on Wednesday afternoon.