A man who was stopped while riding a stolen scooter about 4 a.m. Monday in Everett told the officer there was a grenade under the seat.
Officers saw what looked like a grenade and sealed off the area in the 10800 block of Evergreen Way for the bomb squad.
Experts determined the grenade is inert -- harmless.
Police say the 26-year-old rider was arrested on outstanding warrant and for investigation of possessing a stolen vehicle.
The scooter is being returned to its owner.