Twenty-two children from Cattell Elementary School were taken to a downtown Des Moines hospital on Thursday afternoon after they became sick, school officials said.

No immediate cause for the illness was reported, but authorities said they had ruled out exposure to carbon monoxide.

Phil Roeder, a spokesman for the Des Moines Public Schools, said that around 1:30 p.m. a group of mostly fifth-graders in a physical education class began to demonstrate symptoms that ranged from lightheadedness to nausea to vomiting. He said a couple adults also showed symptoms.

"It was very, very apparent right away that something was wrong," he said.

Roeder complimented a school nurse for quick action and said most of the students were rushed by school bus to Methodist Medical Center in Des Moines. He said parents were contacted immediately.

"At this point in time we're still trying to identify just what the cause of this was," he said.

Dr. Steve Stephenson said a few children were administered oxygen and intravenous liquids, and that most of the students were getting better quickly. He said the simultaneous illness "certainly suggests it was something environmental."

Hospital spokeswoman Jennifer Perry said all but two of the children had been treated and released from the hospital by Thursday night.

Officials said a hazardous materials team was at the school to conduct testing.

Cattell Elementary School is northeast of downtown Des Moines and has about 450 students in kindergarten through fifth grade.