Long Beach police officers were called around 3:25 p.m. to the 6400 block of Marina Drive, the LBPD's Allison Gallagher told City News Service.
Second Street was closed from Naples Plaza to Pacific Coast Highway while the bomb squad examined the device.
A photo published on Twitter by the bomb squad showed an object that looked similar to a hand grenade, but police did not immediately provide a further description.
About 6 p.m., the LBPD tweeted: "LASD Bomb Squad rendered the device safe. Roads have re-opened. The investigation is ongoing."
Further details about the nature of the device were not immediately released.