Updated

More than 20 people, mostly band members, were hospitalized Friday night after suddenly falling ill during a high school football game in southwest Houston on Friday night.

It was first believed they had been exposed to an unknown chemical, but fire officials said later they had found no trace of gases or chemical agents at the scene.

Austin and Yates high schools were playing at Barnett Stadium when, sometime around 9:00pm local time, students suddenly fell ill and hazmat teams and emergency crews were dispatched to the stadium, myFOXhouston reported.

The victims, mainly band members and dancers from Austin High, were reportedly suffering from nausea, vomiting and heart palpitations.

David Almaguer, Houston Fire Department assistant chief, told KTRK-TV that the victims had been taken to several local hospitals.

"A number of the students were complaining of nausea," he said. "We ended up with 22 students being transported to five different hospitals"

A hazmat team was set up a decontamination unit in the vicinity of the stadium, which was evacuated following the incident, KPRC-TV reported.

A student told myFOXhouston he began to smell something odd when he saw his sister lose consciousness.

Another witness told KTRK-TV, "Three dancers moved to the side and started throwing up, then as we got to the stands, more started falling."

A doctor who interviewed patients at the scene said investigators were still trying to work out what caused the students to suddenly become ill, after fire officials said their detection equipment had found no sign of gases or chemical agents in the area.

"The kids all ate at different places, some of them ate at different times ... but they did have something in their stomachs. At this point, it remains a little unclear what set it off," Emergency Medical Services doctor David Purse said.

Click here to read more on this story at MyFoxHouston.

Newscore contributed to this report.