Chemical Fumes caused dozens of children to become ill at Ericson Elementary in Fresno.
The noxious odor came from a nearby apartment complex.
KSEE24's Lemor Abrams is live near Ericson Elementary to update the condition of the children and how the fumes got into the school.
Anxious parents converged after getting word of an emergency.
"It's horrifying. I'm not sure what's going on, Kang Thao, whose kids attend Ericson.
At first, six kids complained of flu-like symptoms including nausea, throwing up, and soar throat...and those kids filed into the nurses office after lunch.
Paramedics arrived to treat them, but then the number grew to 40 sick kids.
And a lunch-time aid, who was the only one taken to the hospital according to firefighters.
"My nephew has a medical condition because if he gets sick by chance he's going to end up in the hospital" one mom told a police officer.
Firefighters say the chemical odor came from a substance used to resurface a pool at the apartment complex next door. And it was blown in through the air air-conditioning vents.
"County Health will be evaluating whether the company that was doing the treatment was operating within the compliance of the chemicals being used," said Deputy Chief Ted Semonious of the Fresno Fire Department.
Hazmat crews say common chemcials were used known as Syrene and Methyl. And they say they're semi-toxic. But with a smell strong enough to sicken kids, and worry parents.
"We only contacted of students that where ill...showing signs," said Susan Bedi of the Fresno Unified School District.
Many parents showed up to school to find fire and police crews blocking streets, and their children still inside.
"It would be nice if they would let us all know what went wrong," said Kang Thao.
Psychologists will be on campus Friday to relieve any anxieties students, teachers, or parents might have.