Provo, Utah ? Trudging through snow far deeper than they expected, rescue crews Saturday searched for three snowboarders feared dead in an avalanche, but found no trace of them.

The search over 10 acres covered with more than 16 feet of snow was exhausting, and not just for humans: Some of the rescue dogs’ hind legs were rubbed raw by ice as they tried to detect the scents of the young men lost Friday in a backcountry canyon in northern Utah.

Search crews “are putting these 10-to-12 foot poles down, and they are not hitting bottom,” Utah County Sheriff Jim Tracy said. At times, the poles couldn’t reach the ground even after rescue crews dug holes six feet deep in the snow, which had a consistency likened to wet cement.

Rod Newberry, 20, Adam Merz, 18, and Mike Hebert, 19, had been snowboarding with two friends Friday afternoon when the avalanche swept down Provo Canyon. Their friends survived, but Newberry, Merz and Hebert were gone.

None of the snowboarders carried standard avalanche safety equipment such as radio transmitters, shovels or probe poles, Tracy said.