LA GRANGE, Ill. (CBS) — A police SWAT team responded to the north campus of Lyons Township High School in La Grange after an instructor reported — mistakenly — she had possibly heard gunfire.

Police from La Grange and nearby suburbs evacuated the high school as a precaution. But in the end, the response was a practice drill for authorities.

“We are going to react to benefit our students and staff safety at all times. We’re going to take every precaution necessary, and that’s what we did today,” Kilrea told CBS 2’s Mike Parker.

The teacher called 9-1-1 around 4:10 p.m. when she thought she heard a gunshot in one of the buildings, CBS 2’s Mike Parker reports.

SWAT teams soon moved into place. The ensuing search disrupted activities, including swim class, club meetings and rehearsal of a student production of “Dracula.”

Lucien Martinez and his fellow soccer players were held on a bus outside the school as police searched. He said he was worried that something was amiss.

But everything was OK. The police search ended at 6 p.m. – a false alarm.

“There were no reports of holes in any buildings, no injuries, no smell, no odors that would be consistent with gunshots,” La Grange Police Chief Michael Holub said.

Police said they do not fault the teacher.