
The police said that the bikers collided with cars as the car drivers suddenly used brakes to slow speeds of their vehicles in the northbound lanes near Wilsonville, south of Portland.
After the incident, bikes scattered across the roadway and two bikers sustained critical injuries.
Police said that rescue teams reached the spot in helicopters and took them to Portland hospitals. Police said that seven others, who suffered shoulder, hip injuries, and broken bones, were given treatment in the hospital.
Traffic on the road was restored at 6 pm.