At approximately 3 a.m. Wednesday, another mudslide brought more trees and debris pouring onto Going-to-the-Sun Road in Glacier National Park, clogging culverts and again turning a 50-yard section of the pavement into a river for an hour or more.

For a third straight day, the iconic highway was closed to all but essential traffic on the west side of the park near the Apgar Campground.

But a Wednesday afternoon helicopter flight over the mountainside revealed what was behind the mess:

Blame some busy beavers.

Park spokeswoman Margie Steigerwald said rangers determined that massive amounts of rain earlier this week caused a large beaver dam to fail.

“It explains all the logs and debris on the road,” Steigerwald said. “I don’t know what happened to the beavers, but it’s good news because it means it’s not a failure of the slope.”