The incident unfolded just before 4 a.m. when police pulled over a 26-year-old man who was riding a Vespa scooter in the 10800 block of Evergreen Way, said Aaron Snell of the Everett police.
Officers then learned the man had several warrants out for his arrest. As he was being taken into custody, he blurted out that there was a grenade under the seat of the scooter. Police at the scene then spotted something that looked like a grenade.
Officers closed down three southbound lanes of Evergreen Way as a precaution and called in a bomb squad to investigate.
The bomb squad arrived at about 5 a.m. and took away the device. They later determined it was a fake.
Police also discovered that the scooter was stolen from Seattle. It was impounded and will be returned to the owner.
Police say the 26-year-old rider was arrested on the outstanding warrants and for investigation of possessing a stolen vehicle.
All lanes of Evergreen Way were reopened in time for the morning commute.