A Novato resident brought the bomb into the Police Department on Machin Avenue at 11 a.m.
Police said the resident found the bomb earlier this morning near the side of the road at Olive Avenue and Deer Island Lane.
The bomb was about 8 inches long and in a plastic tube with a silver metallic powder inside.
Police said officers immediately closed the Police Department lobby and Machin Avenue to vehicles and pedestrians.
The Police Department and Machin Avenue have since reopened.