Riverside police said the crew working at 5625 Magnolia Ave. discovered the device about 7:45 a.m. Tuesday and alerted authorities, The (Riverside) Press-Enterprise reported Wednesday.
"Officers blocked area streets around the location, and residents could not enter the area for approximately 1 hour," Lt. Jaybee Brennan said in a written statement. "The device was found to be an inert World War II-era ... aerial practice bomb.
"The length of time the device was abandoned at the residence is unknown."
Police sealed the area off while the device was being inspected by bomb squad personnel, the Los Angeles Times reported.
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