A police security review at Windham High School went awry Thursday morning when one officer unexpectedly ordered a group of students in the cafeteria to get on the floor.

The officer, one of five conducting a walk-through inspection, told the students in the study group, “This is a drill, this is a drill, please get down,” said Kevin Schofield, Windham’s police chief.

Schofield said the other officers on the walk-through found out what had happened a few minutes later and told the students that there was no drill and they shouldn’t have been interrupted.

No one was injured in the incident, Schofield said, but some of the students were upset. The officers on the scene, Schofield said, apologized to the students and explained what they had been trying to do.

“I’m sorry, and the police officer (who told the students to get down) is sorry that this happened,” said Schofield, who blamed a communications mix-up for the incident.

A lockdown drill had been scheduled for Thursday, he said, but was canceled because of two snow days cutting into school time this week. He said his department decided instead to do a walk-through with five officers, including the school resource officer, to familiarize themselves with the school and perform checks such as making sure they had keys to locks throughout the building.

But even a lockdown drill, which is conducted to make sure emergency measures are in place, would not have included ordering students to the ground, he said. That would occur only if the police had been conducting a “full-fledged active shooter drill.”

Schofield said he would conduct a review to find out “what and where the breakdown in communications happened” and said he couldn’t rule out disciplinary measures for some of the officers involved.

A call to school principal Chris Howell was not immediately returned Thursday.