A middle school in Orlando, Fla., was evacuated Monday after a small bomb exploded in the girls' locker room, according to Local 6 News.

Investigators said coaches at Memorial Middle School were walking through the girls' locker room and spotted a device that had already exploded.

Detectives believe the explosive was thrown through a window and caused a small fire sometime over the weekend or early Monday.

It was not determined what type of device was thrown into the building, but it was deliberately thrown, according to officials.

"The device was thrown through a window and it was possibly an incendiary or explosive," Orange County fire Asst. Chief Rudolph Johnson said. "It went through a window and hit a heater and dropped to the floor. The device caused some moderate burns to the floor and walls."

The school was evacuated Monday morning as a precaution.

Police are trying to determine when the device was thrown and who threw it.

A bomb-sniffing dog was deployed to the school early Monday afternoon.

If you have any information concerning this crime, you are urged to call Crimeline at (800) 423-TIPS.

Watch Local 6 News for more on this developing story.