Fearing a buildup of carbon monoxide, authorities shut down the school.

Emergency responders treated 60 people -- 57 of them kids -- for dizziness and nausea and headaches.

Several students and three adults were taken to nearby hospitals for further observation.

• 11 victims were taken to McKee Medical Center
• 21 victims were taken to Medical Center of the Rockies
• 11 victims were taken to Poudre Valley Hospital

Another 17 victims were treated at a staging area in front of the school.

Loveland Fire Division Chief Merlin Green said the patients had a sudden onset of illness around 10 a.m.

"I just got dizzy, then my stomach kind of hurt and if felt like I was going to throw up," said Valeria Torres, who was treated for nausea.

Parents were notified about the emergency via phone call.

Valeria’s mom drove to the school then to a nearby assisted living center and back to school frantically searching for her daughter.

“They told me she was taken to a hospital,” Paula Velasquez said. “But they didn’t say which one.”

“It’s kind of frustrating because you’re scared,” Velasquez said. “We knew she was at the hospital and no one’s telling us which one. Finally an EMT (emergency medical technician) was able to tell me which hospital she was taken to.”

Carol Zugarramurdi learned about the emergency from a friend who happened to drive by the school and saw Zugarramurdi’s grandson sitting on the curb with an oxygen mask.

“That scared me because I didn’t know what was going on,” Zugarramurdi said. “Of course I rushed over here.”

Both her grandson and her granddaughter were transported to a nearby hospital after complaining about headaches, dizziness and nausea.

“They gave me these tablets that like dissolved on my tongue and gave me some Tylenol and it helped me,” said 10-year-old Candi Zugarramurdi.

“We just rested a while and they took our vitals a lot,” added 11-year-old Cisco Zugarramurdi. “After a while we started feeling better.”

What caused the sudden illness among the students and staff is still a mystery.

When asked if it may have been carbon monoxide, Green said, “We don’t know. We conducted air monitor tests inside the building, but detected nothing out of the ordinary.”

Loveland Fire & Rescue and Xcel Energy cleared the school and the surrounding area early Tuesday afternoon, after finding no apparent cause for the reactions.

Children who showed no symptoms were taken to the Marisol Senior Living Center at 1153 Finch St., said Melissa Adams, spokeswoman for the Thompson School District. Parents were directed to pick up their children at the senior center.

School was canceled for the rest of the day.

The school will reopen for normal operation on Wednesday. Parents have been notified.

The building will be re-inspected, including air sampling, at 5 a.m. to ensure the safety of all its occupants.