As night fell, as many as 30 people were thought to be still inside the wreckage of the Hotel Rigopiano, Italy's Civil Protection Department said. Some could have survived in air pockets, officials said, although cold temperatures would endanger any survivors.
The avalanche swallowed the four-star hotel, at the foot of the Gran Sasso mountain about (135 kilometers) 85 miles northeast of Rome, Wednesday night after a series of earthquakes in the region that day.
Road crews had cleared much of the snow and fallen trees by nighttime Thursday, finally allowing heavy rescue equipment to reach the hotel. Snow machines and helicopters had earlier taken searchers, including dogs, up the mountain.
Officials based estimates of the missing on guest registration and staff numbers, but said it was possible that some people had escaped before the avalanche hit.
The hotel has 43 rooms, according to website TripAdvisor.
Italian fire department spokesman Luca Cari, who was at the scene, told CNN that the hotel had been "completely slammed" in the avalanche and debris was scattered as far as 100 meters from the hotel structure, making the search area large.
Two people were rescued from the site of the hotel, Civil Protection Department chief Fabrizio Curcio told journalists, but rescuers using search dogs have otherwise seen no sign of life.
"We are calling out but no one is answering," a searcher told Italian state media ANSA.
One man, vacationing with his wife and two children, 6 and 8, said he missed being caught in the destruction only because he had walked to his car just before the avalanche hit. The whereabouts of his wife and children remained unknown Thursday.
Firefighters told ANSA the hotel had been "swept away" and buried by tons of snow, and that there were mostly uprooted trees and debris at the hotel site. Two bodies had been recovered more than 24 hours after the avalanche hit.
An elderly farmer also died in the same region of Abruzzo on Wednesday when his barn collapsed
Rescuers ski to disaster zone
Video recorded by rescue teams showed what appears to be a smashed wall or window in the hotel's lobby, with tree branches, snow and other debris piled on the floor.
Curcio explained that dealing with earthquakes and an avalanche at the same time caused difficulties in the rescue operation and even confusion among the affected population over how to respond.
"For the weather, you tell people to stay in their homes, while for the earthquake, citizens must be brought outside. Putting together these two elements is extremely complicated," he said.
Rescuers battled blizzards and strong winds to reach the site, some having to ski for several kilometers in the darkness to get there because some roads were impassable.
When they arrived, they found only the building's top story and roof visible above the snow, Italy's Mountain Rescue Service said on social media. It also posted a picture of rescuers digging for survivors.
Italy's fire department posted a photo on Twitter showing rescuers being dropped into the area by helicopter.
Italian Prime Minister Paolo Gentiloni said the amount of this week's snowfall in the country is something that hasn't been seen in decades.
CNN Meteorologist Brandon Miller said heavy snowfall in the last 24 hours measured 70 centimeters (nearly 28 inches) and over the past week, snow accumulations were more than 3 meters (about 10 feet) in the mountains. The risk of more avalanches is high, he said.
"The recent, historic snowfalls have created a very loose and unstable snowpack, which is why the avalanche danger is high on all steep slopes."
Rescue efforts ongoing
Rescuers were still trying to get to other areas isolated by the avalanche, Gentiloni said, and authorities were hoping to bring power back to as many as 90,000 people who were left in darkness overnight from the extreme weather.
Central Italy was rocked by more than 10 earthquakes Wednesday, four of them above magnitude 5, according to the US Geological Survey.
An initial 5.3-magnitude quake hit in the morning near the town of of Amatrice, which was devastated by powerful earthquakes in August. The tremors continued for more than six hours, with one as strong as magnitude 5.7.
While the epicenter was 90 kilometers (about 55 miles) northeast of Rome, the quake was felt in the capital, sending people running from buildings in a panic.
All the aftershocks hit around Amatrice, in the mountainous regions of Marche, Lazio and Abruzzo.
Nearly 300 people died in the August earthquakes in central Italy around Amatrice, leaving
its town center -- once popular with tourists -- reduced to rubble.