WILLIAMSON COUNTY, Tenn. (WKRN) – At least 10 people were taken to the hospital after being exposed to what authorities are calling an “unknown substance” in the Williamson County Detention Center.

The Williamson County Sheriff’s Office said at around 2:30 p.m. Wednesday, deputies were made aware of an incident involving inmates being exposed to an unknown substance. At least 10 people, including inmates, staff, and emergency responders, were taken to Williamson Medical Center for treatment and further evaluation.

Out of an abundance of caution, several additional employees and about 24 inmates in the immediate area of exposure underwent a “decontamination process” with help from emergency personnel on-site, according to investigators.

Just after 6:30 p.m. Wednesday, the sheriff’s office said everyone who was taken to the hospital had been released. All facilities have been sanitized and are resuming normal operations.

On Thursday, the sheriff’s office said their initial investigation revealed the substance was powdery and field-tested positive for fentanyl. The substance has been sent to the Tennessee Bureau of Investigation for confirmation.

“We will continue to investigate the incident and are thankful that everyone involved is okay,” Sheriff Dusty Rhoades said.