The week's torrential rain caused three mudslides Tuesday night that closed the road to Yellowstone National Park's east entrance for most of Wednesday.
Two smaller mudslides were able to be cleared, but one 300-foot wide slide closed the highway in the Shoshone National Forest all Tuesday night.
One lane opened Wednesday. Crews have been working all day to clear the slide.
However, the mud keeps coming down and it's carrying large tree trunks with it, making clean-up efforts difficult.
Park officials say the slide, which is three miles outside of Yellowstone, carried one car down the road and wiped out an access road to cabins.
Crews expect to remain on site all night to keep one of the lanes open.
Official said heavy rain in the mountains caused the already saturated soil to flow across the highway.