SNOHOMISH — Loose logs spilled and splintered across U.S. 2 on Monday morning when a log truck crashed near Snohomish, causing serious injuries and shutting down an arterial route.

Five vehicles and a loaded log truck from Yakima-based Wyss Logging collided around 11:20 a.m. east of the interchange with Highway 9, said trooper Heather Axtman of the Washington State Patrol.

Four vehicles ended up in dry grassy ditches on both sides of the road: the red semi tractor and its trailer; a white work van of a Monroe electrical company; a white Chevy pickup; and a Lincoln SUV that flipped onto its roof, a good distance from the others. A Toyota pickup truck covered in bumper stickers came to a rest on the road, with a mangled front end.

One woman was flown out on a medical helicopter due to critical injuries, Axtman said. At least one other person needed medical aid for difficulty breathing.

U.S. 2 was shut down in both directions for about 3 miles between Highway 9 and 88th Street SE. Traffic was detoured through Snohomish. The main route from Everett to Stevens Pass remained closed for hours.

Troopers were collecting evidence and interviewing witnesses at the scene. They suspect a driver of one of the passenger vehicles crossed the center line and caused a head-on crash with the log truck, Axtman said.

Tens of thousands of pounds of logs needed to be cleaned up.

Caleb Hutton: 425-339-3454; chutton@heraldnet.com. Twitter: @snocaleb.