LOGAN — Crews searching for a mother and her two children believed to have been buried and killed under several feet of mud that slammed into their rental house indicated they had made "good progress" Monday.

The operation focused on the house's back bedrooms. At the beginning of the day, 15 feet of mud, dirt and debris was piled on top of that region. By noon, Logan public works director Mark Nielsen said crews had dug to within two feet of where they believed the bedrooms were. From that point, 5-gallon buckets and a chain of people were used in the search rather than backhoes.

Nielsen hoped to have the situation resolved "by the end of the week."

Meanwhile, there were plenty of questions surrounding why the tragic slide happened, who, if anybody, was responsible and could it have been prevented?

"I wish I could give you an answer," Nielsen said when asked about why the slide happened. "We don't know why it slid."

Jackeline Leavey, 43, her son, Victor Alanis, 14, and daughter Abbey Alanis, 12, were believed to be inside the house they had only been renting for a month when their landlord told them to evacuate. But before they could get out, the mudslide hit without warning.

Members of the media were taken to an area Monday where they could get a closer look at the operation. There was no evidence of a house where the structure once stood at 915 E. Canyon Road. Trees were being cut down and mud removed from the hillside Monday. Above the house were concrete remains of the canal that burst and sent a fatal mixture of mud and water to the homes below with such force that one house was knocked 20 feet off its foundation, according to officials. The slide happened in an area known as "the Island," near the campus of Utah State University.

What remained unclear Monday was whether the canal was solely responsible for the tragic events. Owners of the canal, who were on scene Saturday, told Logan officials they don't believe it was.

"(They said) 'We don't know what happened. We're concerned. We're sorry.' They did not believe it was due to their canal," Nielsen said.

One possible explanation offered Monday was a slide prior to the one that knocked out the home.

Francis Ashland, senior geologist with the geological hazards program at the Utah Geological Survey, has been at the hillside since Saturday. He said there was a slide on the lower slope, below the canal and above the house, that compromised the canal itself, causing to break which in turn caused the large destructive slide on the upper slope.

What caused the lower slope slide, however, was unknown Monday. Ashland said there were three possible factors: