(CNN) Two 14-year-old girls in Florida have been arrested after a teacher discovered their plans to kill nine people, sheriff's reports say.

The Highlands County School Board confirmed in a statement to CNN that two Avon Park Middle School students were taken into custody Wednesday for "a possible plan to harm others off campus," but declined to offer additional details, citing the ongoing investigation.

Avon Park is about 80 miles south of Orlando.

A teacher saw the two girls acting "hysterical" while they searched for a folder in her classroom, according to the girls' arrest reports from the Highlands County Sheriff's Office.

The girls were concerned that they could be arrested, the teacher told police, and one of them said, "I'm just going to tell them it's a prank if they call me or if they find it."

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