A four-mile back up remains on southbound Interstate 5 at Highway 104, near Mountlake Terrace, though all lanes have now reopened. Four lanes had been blocked by the early Monday morning collision and emergency responders, according to the Washington State Department of Transportation.

A collision blocked four lanes of traffic on southbound I-5 Monday. (Courtesy of Washington State Department of Transportation.)
A collision blocked four lanes of traffic on southbound I-5 Monday. (Courtesy of Washington State Department of Transportation.)