Two people have been arrested and charged after seven Virginia elementary students ate gummy bears from a plastic baggie that later tested positive for the potentially deadly synthetic opioid fentanyl, the Amherst County Sheriff’s Office said Wednesday.

At first, it seemed the students were having an allergic reaction to something they ate Tuesday, Amherst County Public Schools said. The sheriff’s office conducted a field test of the bag, which had “a positive reaction for fentanyl,” the school district said.

“Preliminary investigation shows the students ingested gummy bears from a plastic baggie. In that baggie contained a residue, and the residue tested positive for fentanyl,” sheriff’s spokesperson Lt. Dallas Hill told CNN.