PORTLAND, Ore. (AP) — Two backcountry skiers were killed and two others were seriously injured when an avalanche in eastern Oregon's Wallowa Mountains hit a party of eight, officials said.

The deaths mean at least 12 people have died in avalanches nationally this season, including six since Sunday.

Low clouds and poor visibility grounded a rescue effort for the injured skiers late Tuesday night, Baker County Undersheriff Warren Thompson said. Two medics were with the man and woman.

Four unhurt skiers were being brought out by snowcat, a large tracked vehicle that can maneuver on snow, Thompson said.

The snowcat was unable to reach the injured skiers because of the incline of the slope they were on, the undersheriff said. The injured woman suffered two broken legs and a shoulder injury while the man had a broken thigh bone, Thompson said.

Two National Guard helicopters, one each from Oregon and Idaho, hoped to resume rescue efforts Wednesday, Thompson said. They spent the night at the Baker City Airport. Ground rescue crews also worked to get closer to the site.

Most of the skiers were from the Seattle area. Officials weren't releasing names until relatives could be notified.

The avalanche hit at about noon Tuesday as the eight skied in the remote and mountainous area near Cornucopia, Baker County Sheriff Mitch Southwick said in a statement.

Connelly Brown, the owner of Wallowa Alpine Huts, said the skiers were part of a backcountry skiing group organized by his Joseph-based company. The group included two guides and six skiers.

Brown said a guide contacted him by cellphone after the avalanche hit, reporting two possible fatalities and two skiers with broken legs. The skiers were on a guided five-day, four-night trip, he said.

The avalanche came down on the third day of the trip, Brown said. Later that night, as on previous nights, the group planned to sleep at the Schneider Cabin, a historic miners' log cabin on the south side of Cornucopia Peak.

Brown said the clients and the guides were all "fit, proficient downhill skiers." The guides were certified by the American Institute for Avalanche Research and Education and trained by the American Mountain Guide Association, he said.

"From the description, it sounded like they were traveling and the avalanche came from above and caught them by surprise," Brown said.

The avalanche occurred in the southern part of the Wallowa Mountains, near the Idaho border. The Wallowas are known as the "Alps of Oregon." With their rocky peaks and deep ravines, the mountains are popular with backcountry skiers, hikers and horseback riders.

A bulletin from the Wallowa Avalanche Center on Thursday warned that "new snow is not bonding well to the old surface." The bulletin mentioned a recent report from the southern Wallowas of a skier triggering a small avalanche in which no one was caught.

Elsewhere, Kevin Kuybus, 46, of Highlands Ranch, Colo., was found dead Tuesday after an avalanche outside a Colorado ski area. Another avalanche near Kebler Pass, Colo., killed a snowmobiler Monday.

The death toll includes two people who died in slides in Utah over the weekend. On Sunday, Ashleigh Cox, 21, of Colorado Springs died after being caught in an avalanche while she was snowshoeing Saturday in American Fork Canyon. About 90 miles away in Sanpete County, Clint Conover, 36, died after being buried in a slide Sunday while snowmobiling.