Four cars were struck by gunfire Wednesday afternoon on state Route 509 in Des Moines, according to the Washington State Patrol.
The highway is closed near South 160th Street in King County while troopers search for the shooter, the State Patrol posted to Twitter about 2:30 p.m.
Additional shots have been fired since the initial incident, troopers say, though no injuries have been reported.
Motorists are advised to stay away from the area as a police investigation continues. Detours have been set up in the area.
Law enforcement finished an area search about 6:15 p.m. and reopened the southbound lanes of SR 509, though the right-hand northbound lane remains closed as K-9 units are used to seek further evidence from the shooting scene. The search for evidence went well into the evening hours before the highway fully reopened about 8:30 p.m.