"Could they be alive?" asked Dr. Terri Schmidt, physician supervisor for American Medical Response in Clackamas County, Oregon. "Yes. Is it very likely? No."

Luke Gullberg, left, Katie Nolan and Anthony Vietti went hiking on Mount Hood. Gullberg, 26, was found dead.

The specialist in emergency medicine noted that time is not in their favor. "What we know is that at about 48 hours -- two days -- the chances of finding somebody alive after that go down to about 1 percent."

She added, "At some point, we have to say it's time."

Still, she said, Anthony Vietti, 24, and Katie Nolan, 29, have several factors in their favor: "They're young; they're healthy; they -- as far as we can tell -- are relatively experienced and relatively well-equipped."

The body of a third hiker, 26-year-old Luke Gullberg, was found dead Saturday from hypothermia.

Clackamas County Sheriff Craig Roberts said Tuesday that, despite the odds, the the search operation had not moved into a recovery operation.

In fact, the search was not continuing in any form. Operations coordinator Nate Thompson bemoaned the heavy snow that fell over the weekend and forced the suspension. "A lot of our clues are now covered," he said.

Steve Rollins, a team leader with Portland Mountain Rescue, said the avalanche danger would not permit rescuers to venture out any time soon.

"Slopes that do not normally avalanche are avalanching now," he said. "I don't see that we're going to have conditions that will permit us to put anybody safely on the ground in the foreseeable future."

Thompson hypothesized that the hikers may have been involved in an accident and that Gullberg, the most experienced of the hikers, may have broken away from the others and begun to backtrack in an effort to seek help.

Above his body, rescuers found a water bottle, a helmet, a harness, a camera and camera case and a mitten belonging to Nolan.

"Maybe Katie lost a mitten in an accident," Thompson said. If Gullberg did indeed seek to return for help and Nolan lost one of her mittens in an accident, he may have left his gear, his pack and his supplies and gloves with her, taking the lone mitten, he said.

But descending can be more difficult than climbing in some places. "If there was some form of an accident and Luke did downclimb, this is a much more difficult descent," he said.

National Weather Service meteorologist Charles Dalton told CNN that some 15 inches of snow had fallen at an altitude of about 6,000 feet between Monday and Tuesday afternoon, when temperatures were just below freezing.

The three hikers, all from the Pacific Northwest, set out at about 1 a.m. Friday (4 a.m. ET), on what was to have been a fairly easy, "semi-technical" hike in which they would have descended the south side of the mountain, said Deputy Scott Meyers of the Clackamas County Sheriff's Office.

Vietti's home is Longview, Washington; Nolan's is Portland, Oregon. Gullberg was from Des Moines, Washington.

Gullberg's MySpace page is filled with photos of him hiking in various places.

The mountain rises 11,239 feet above sea level, with a base that stretches across 92 miles (148 km). It is the highest mountain in Oregon. Mount Hood is a dormant volcano with steam constantly spewing from holes, according to the Web site mthood.info.