Washington State Patrol says a portion of Interstate 90 near Mercer Island has reopened after it was closed for several hours.
The two right lanes of westbound I-90 remain blocked at this time, but all eastbound lanes are back open.
A bomb squad is on the way to investigate what appears to be an explosive device that a driver threw onto the highway.
It happened while Bellevue police tried to stop a vehicle that entered the highway heading westbound.
Bellevue police have two people in custody.
KIRO 7 News is headed to the scene and will update this story as soon is more information is available.