(Mt. Hood, OR) -- Crews are battling a new wildfire southeast of Mt. Hood. The Boulder Fire started Saturday near the Boulder Lake Trailhead. It's grown to 100 acres and it's burning in heavily forest areas on steep slopes. Four Hotshot crews, two helicopters and other ground crews are working to build containment lines. Several campgrounds are under Level 3 Go Now evacuations. An investigation into the cause of the fire is ongoing.