The FBI has joined the investigation after police evacuated a Civil War re-enactment site in Middletown, Virginia, on Saturday when a suspicious item was found.

The Frederick County Sheriff's Office said someone found the item at the Cedar Creek Civil War re-enactment about 4 p.m. Officers evacuated the immediate area and set up a safe zone, the sheriff's office said.

Several police and fire agencies responded to the scene as well as the Virginia State Police Bomb Squad, which "rendered the device safe," according to the sheriff's office. K-9 units continued to search the entire battlefield.

Police have not said what device was found. The FBI asked that anyone who may have witnessed any suspicious activity or information to contact them.

“Due to this unfortunate situation, our event staff is unable to fulfill the required logistical needs to continue the event on Sunday. It is regrettable that a nice family event would be disrupted in this way,” said Joe D’Arezzo, president of the Cedar Creek Battlefield Foundation.

Someone said in a letter earlier in the week that they would harm "attendants of this event," prompting police to provide additional security.