A passenger reported finding the unattended package and alerted authorities just after 7 a.m.
Officers responded to the scene and evacuated the bus. A bomb squad, two SWAT teams and two robots were called in as the entire business district at 240th Street and 104th on Kent's East Hill was evacuated as well.
Streets were closed in the area and bus service was rerouted. About three hours after the package was found, the air space over the bus also was closed off to aircraft, including news helicopters.
KOMO News reporter Keith Eldridge, reporting from the scene, tweeted, "SWAT vehicles now front & back of Metro bus. This is not your normal suspicious backpack episode."
But soon afterward, a robot shot the device and officials determined it was left over from an earlier bomb training drill.
Emergency responders left the scene and business were reopened by noon.