Authorities in Texas are investigating what sent nearly two dozen people at a high school football game to the hospital.
At least 22 people complained of nausea, coughing and scratchy throats during a football game between Yates High School and Austin High School at Barnett Stadium in Houston Friday night.
"The people that we saw and transported were mostly the students that were in the drill team or the band. Nobody in the stands were affected," said Houston Assistant Fire Chief David Almaguer.
Houston Fire Department initially suspected the students were exposed to an unknown substance, possibly chemical related, according to ABC News station KTRK.
Almaguer said the hazmat team did not find anything unusual and they are now looking into other causes.
"They mentioned that they had a blood drive today at the school there were some other things and that's why they are sending them to the hospital," he said.
A doctor from the EMS service told KTRK Friday that they were interviewing patients to find out the cause.
"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," Dr. David Purse told KTRK. "It's still a mystery right now."
ABC News Radio contributed to this report.