Calaveras County Sheriffs investigators are trying to determine the cause of an early morning explosion that rocked Rail Road Flat.

Deputies and fire personnel were called to the Railroad Flat Store around 1:30 a.m. Monday morning after they received several reports of an explosion in the downtown area.

Law enforcement officials say they found evidence that some type of explosive device was detonated in front of the store, damaging the store, breaking windows and causing minor damage to Railroad Flat Elementary School and other nearby buildings. The school was close Monday but will reopen Tuesday.

There were no injures and no fire from the explosion.

According to sheriff’s department spokesperson Debi Parsons Monday afternoon, no new information is being released. The cause and nature of the explosion is still under investigation