Crews were making progress Sunday at clearing away a rock slide that had isolated the northeastern corner of Yellowstone National Park, but no estimate was given as to when the road between Mammoth Hot Springs and Tower Junction would be reopened.

The rock slide came down sometime early Saturday and closed a section of the park's Grand Loop Road about eight miles east of Mammoth Hot Springs near Blacktail Plateau Drive, a park release said. At the same time, deep snow on Dunraven Pass continues to prevent traffic between Tower Junction and Canyon Village.

"While enough debris has been cleared from the road to allow for emergency travel if necessary; park managers remain concerned about several car-sized boulders perched atop unstable material at the base of the slope immediately adjacent to the roadway," the release said. "The park is planning on additional investigation by geo-technical consultants, and considering work to be performed by a contractor which may be needed to safely reopen the road to travel.  This section of road will remain closed for several days."

Visitors can still reach the park's northeastern corner, but they need to take US-212 to US-296 to WY-120, the route linking the communities of Cooke City, Montana, and Cody, Wyoming.

To improve access elsewhere in the park, crews and plows that had been working to open the Beartooth Highway to the east of the park's Northeast Entrane were sent to work on clearing the snow on Dunraven Pass, the park release said. If conditions allow, this section of road could be open by next weekend, the release added.

Park crews were also working to clear and repair the Blacktail Plateau Drive, a one-lane gravel seasonal scenic route that parallels the section of road closed by Saturday’s rock slide, park officials said. While not suitable for heavy visitor traffic, if opened it would allow for safer emergency travel and limited administrative travel to resupply the Yellowstone General Store at Tower Fall, and support efforts to open Roosevelt Lodge on schedule on Friday, June 10, they added.

Meanwhile, Yellowstone remained under a winter weather advisory until Monday morning, with falling and accumulating snow reported Sunday across most of the park. Visitors were told to be prepared for temporary road closures due to snow and ice.

The North, West, and South entrances to Yellowstone are open, subject to temporary closures due to weather. Unstable snow conditions and the threat of snow slides continue to limit travel on the East Entrance road through Sylvan Pass to between the hours of 8:00 p.m. and 10:00 a.m.