UPDATE: 4:30 a.m.
Police investigated a possible bomb threat off Bechelli Lane in Redding at around 12:40 p.m. Monday.
They say a U.S. postal worker reported a suspicious device in a mailbox cluster in the Mission Square shopping center on Bechelli Lane in Redding.
Police closed off the parking lot of the shopping center to traffic for several hours while they investigated.
The Shasta Bomb Squad was called to the scene and determined the device was not an explosive at around 4:30 p.m.
Redding police chief Roger Moore says the device was recovered and taken in for further investigation. The device was determined to be a training grenade.
Fingerprint samples were taken. Investigators are trying to determine who left the training grenade there, and for what motive.