LAKEWOOD, Colo. -- The Jefferson County Open School in Lakewood was evacuated Monday afternoon after several students there had a reaction to a substance on the playground.
The thing is, officials know there was something in the air, they just don't know what it was.
The school was closed Monday after the incident and it will remain closed Tuesday.
Hazmat workers said a toxic substance was detected, but at such low levels that they couldn't determine exactly what it was. However, they were able to "rule out" fertilizer and any organic contaminants, West Metro Fire said.
All contaminants had disappeared as of 3 p.m., and officials said the school and neighborhood were safe.
Wind was blowing toward the school at about 15-20 mph at the time, meaning something could have blown into the area.
Jefferson Public Schools spokeswoman Michelle Reeves said 31 people were exposed to the substance, exhibiting irritated skin and eyes. 30 of those were students. Seven students were taken to the hospital as a precaution. Everyone is fine.
Emergency personnel set up a tent and the rest underwent decontamination at the school and were then evacuated.
Investigators say there is no reason to believe the toxin was released on purpose.
The JCOS has pre-kindergarten through 12th grade classes about 500 students. It's on W. 10th Avenue and Wadsworth Boulevard.