Washington state troopers and tow trucks worked to clear the area and three southbound lanes had reopened by late Tuesday afternoon.
Kyle Ohashi with the Kent Fire Department says 20 vehicles were involved.
He says weather may have been a factor. He notes the often dangerous combination of rain, followed by a sunbreak and reflection on wet roads.
"We believe this was kind of a classic example we see this time of year where you have wet roads, raining, and then suddenly the sun breaks out and you get all that reflection," he said. "People can't see so they slow down and others unfortunately, do not."
Several other Puget Sound-area freeway crashes were reported as sun mixed with occasional showers.