State troopers responded to the scene, at the south end of Willapa Bay, at about 10:15 a.m. after receiving a report of a semi truck crash.
Arriving at the crash site, they found a semi trailer on its side and thousands of pounds of fish guts spilled over the highway and along the roadside.
Trooper Russ Winger of the Washington State Patrol said the semi truck was enroute from Ilwaco to a plant that processes fish remains into pet food.
He said it appears the fish guts sloshed around inside the trailer, causing it to sway and then tip over as the truck rounded a curve.
A tow truck was called in to remove the semi. But more than three hours later, the north lane of the highway was still blocked by the slippery, stinking mess.
A small notice on the state Department of Transportation's Facebook page said, "At least it's raining."