UPDATE: The white powder found at the courthouse was not lethal, a West Palm Beach police spokesman says.
First responders are investigating the discovery of white powder at the Palm Beach County Courthouse.
The unknown substance was found in the mailroom.
Quadrille and Banyan Boulevards in the vicinity have been closed to make room for emergency vehicles.
According to the Palm Beach County Sheriff's Office the first floor has been evacuated and no one can enter or leave the building while West Palm Beach Fire Rescue investigates.