ST. CLAIR TWP. — A pest-control and weed-killing chemical sprayed Tuesday onto fields behind Edgewood Middle School is likely what caused the evacuation of the building and several students being taken to the hospital, officials said.

Forty-seven kids were affected — 21 were treated, with some taken to area hospitals and most released to parents, said Jeff Galloway, director of Butler County Emergency Management.

Five students were taken to the Cincinnati Children’s Hospital Medical Center in Liberty Twp., and one was transported to the Atrium Medical Center in Middletown, Galloway said Tuesday night. 

The children were transported from the Busenbark Road school for further treatment at the requests of parents, Galloway said.

“We moved all the kids out of here and then evacuated this school, and then we had 26 more symptoms over at the high school, but they’re middle school kids that were moved there” during the evacuation, he said.

Hazardous material teams and numerous emergency crews responded to the scene at the middle school after dozens of students complained of headaches and feeling dizzy, officials said.

The school has used the same pest control company before without problems, but heavy, humid air and a breeze pushed the odor toward the open windows at school, Galloway said.

Galloway said several high-tech monitors were brought in, but they turned up no readings.

“About an hour and a half to two hours into the incident, we discovered that a pest control company came this morning and sprayed the fields — the baseball field and field around the football stadium — out here with some kind of a pest control while the windows were open,” he said.

“What we’re thinking is that chemical and the smell of it went into the classrooms,” he said. “The chemical they’re dealing with is an irritant by inhalation. The symptoms they were exposed to were difficulty breathing, nausea, headaches and dizziness.”

Galloway said blades of grass from the baseball field were tested, confirming they had been sprayed with the chemical Momentum — which kills weeds and clover, but not grass. The chemical is described as slightly toxic with corneal involvement or irritation and moderate skin irritation, according to gardenguides.com.

“We did more of a precaution today by bringing all the hazardous material teams out here and checking. There was a situation here, but I don’t believe it was a life-threatening situation.”

Butler County Sheriff’s Capt. Richard Greer said extra deputies were called to the school, which has about 1,100 students in grades 5-8, to help control traffic in front of the school — crowded with emergency vehicles — as concerned parents showed up to check on their kids.

The odor was first detected in the fifth- and sixth-grade wing, where students started complaining of headaches and coughing at 10:30 a.m., said John Thomas, a spokesman for the district.

Students were allowed back in the school about 1:30 p.m. after officials were told that the building was clear.