State troopers and emergency crews responded to the scene, near Oakesdale Avenue past the Highway 167 interchange, immediately after the 7 a.m. crash.
It took an hour and half to reopen some lanes to traffic, then the freeway's southbound lanes were closed again to remove the semi rig from the scene. Two lanes were then reopened by 10 a.m.
No serious injuries were reported. Some of those in the vehicles involved were shaken up and checked out for minor injuries.
Trooper Karim Boukabou said it appears the semi driver, a 29-year-old Olympia man, was at fault in the incident, colliding with three passenger cars before rolling the tractor-trailer rig onto its side across all four lanes of the busy freeway.
He said it appears the semi driver was distracted somehow just before the crash. He was cited for second-degree negligent driving, an infraction which carries a $550 fine.
Jim Gibbons was driving the car right behind the semi and said it appeared the driver didn't brake in time for slowing traffic in the lane ahead.
Gibbons said he watched in awe as the big rig veered toward the shoulder then back across all four lanes of the freeway as it keeled over and slammed onto its side.
"He came right across the freeway, right in front of me," Gibbons said. "It was like something out of an action movie - I was expecting Arnold Schwarzenegger or somebody surfing on the back of the truck or something like that."
Gibbons said the accident fouled up his morning plans, but he was relieved to hear that no one was hurt. And he says, "I met some new friends out here on the freeway this morning."
He called it "dumb" for the truck driver to be distracted while driving.
Alison Pahl says she was driving through the area when the semi rig slammed into her SUV and crushed its back end. She says she believes the truck driver did all he could to avoid hitting other vehicles.
"I'm very thankful. I think the truck driver did a great job in going off to the side of the road. If he would have hit me head-on, I probably would not be here," she said.
Lewis Hendrickson, whose car was car clipped by the semi truck or some debris, says it was very fortunate that no one was seriously hurt in the crash.
"Maybe a higher power was looking out for us, and we were lucky today," he says. "We're all fortunate to be here. Damage to cars is fixable. Damage to people is not easily, and nobody's damaged - and that's a good thing."
Trooper said later that one car was allowed to squeeze through the accident scene right after the crash because the driver said his wife was in labor.
Heavy equipment was later brought in to move the semi trailer off some lanes and allow some traffic to get through, starting at about 8:40 a.m. Once the blockage was cleared, the southbound lanes were closed down again to allow a large tow truck to remove the semi from the crash scene. Two lanes were reopened by 10 a.m.