San Juan County spokesman Rick Bailey said three people were flown to Colorado hospitals from the school in Montezuma Creek, a small town on the Navajo Reservation about 15 miles west of the Colorado border.
Bailey said one female teacher was being moved from a Cortez, Colo.-hospital to a Salt Lake City-area facility Monday night. It was the closest location with a hyperbaric chamber, which is used to treat carbon monoxide poisoning, he said.
Another female staff member who was flown to a Durango, Colo., hospital was still being held there Monday evening, he said.
A female third-grade student also was airlifted to the Cortez hospital but later was released.
Bailey said another 33 students and staff were taken by ambulance to medical facilities in the Utah cities of Blanding and Monticello. At least eight other people either drove themselves or got rides to treatment centers, he said.
Everyone treated at Utah facilities was expected to be released sometime Monday, Bailey said.
The leak occurred at about 8 a.m. as people arrived at Montezuma Creek Elementary and before classes started. All of the approximately 280 people in the building at the time were evacuated, the San Juan County Sheriff's Office said in a statement.
One emergency medical worker suffered a broken leg during the evacuation after jumping from a wall to get to another part of the school, Bailey said. He had no further details on that incident.
The school remained closed Monday, but officials planned to reopen it Tuesday.
The leak appears to have been caused by a water heater with a blocked ventilation system, officials said.
The school doesn't have carbon monoxide detectors, San Juan School District Superintendent Douglas Wright said.
Deputies said emergency calls came from the school near the Four Corners area with reports of students feeling dizzy and sick. About 10 ambulances and multiple police and fire crews responded.
"It looked like a metropolitan response," Bailey said.
About 200 students attend Montezuma Creek Elementary, according to 2012 enrollment data.
Bailey said school officials and emergency response teams were able to get people out quickly.
"It definitely could have been really a tragic situation," he said.
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