The threat of a potential bomb on the side of Louise Avenue near Garden Gate Drive prompted Manteca Police to shut down the major east-west arterial from Main Street to near the Highway 99 overcrossing for an hour and a half early Monday afternoon. Officers responded to an alert citizen who had found a clear plastic grocery bag at 1 p.m. with wiring to switches and capacitors inside. It had been placed near the curbing on the north side of the roadway just east of the Garden Gate intersection.