At least a half-dozen large rocks fell from a cliff behind the house in Rockville Thursday evening, crushing it and a garage, authorities said.
Springdale Police Chief Kurt Wright said two people were found after a search of the house. Their names haven't been released, but Wright described them as a middle-aged couple well-known in the community.
"It's been tough to see the people show up and crumble into tears. It's been hard for the whole canyon," he told KSL-TV.
Wright said the site was "unstable" and added that crews would assess the situation Friday to determine how to recover the bodies.
The police chief said snow and ice had built up on the cliff and between boulders.
Rockville, which is about 5 miles from Zion National Park, is a common site for rock slides, especially in wet weather.
"We typically do tend to see more rock falls during high precipitation events, rain or snow," Tyler Knudson, of the Utah Geological Survey, told KSL. "The snow melts, gets in joints in the rocks. When it freezes it expands and can trigger rock falls. It is more common in the winter, fall and spring."