Lyons Street was closed for about two and a half hours Monday after the Tuolumne Utilities District reported a suspicious device attached to a fire hydrant near the entrance to the Blackberry Oaks Apartment Complex.
The device was reported by TUD workers at 1:41 p.m. Traffic was diverted around the area.
The police officers who responded at the scene called in the Calaveras County Sheriff's Bomb Unit, which arrived along with the Sonora Fire Department and identified the device as a live military practice ordinance.
It was cylindrical in shape with a pull pin and had been painted from its original color.
The Calaveras Bomb Unit removed the device.
It would have had little shrapnel output if detonated, but would have been as loud as up to half a stick of dynamite, according to the Sonora Police Department.
The investigation into the device is ongoing, the Police Department said.