The landslide hit a residential area north of the capital, Oslo, forcing some 700 people to evacuate.
At least 10 people, including children, are missing after a landslide in southern Norway swept over a dozen buildings in the early hours of Wednesday, police said.
A rescue operation continued overnight with drones and helicopters, police said, adding that at least 10 people were injured in the disaster, one of them seriously.
The landslide struck a residential area in the municipality of Gjerdrum, about 30 km (19 miles) north of the capital, Oslo. Police said 700 people had been evacuated from the area.
Photos from the site showed a large crater with destroyed buildings at the bottom of it. Other buildings were clinging to the edges of the crater, according to TV footage.
Two more houses collapsed in the crater on Wednesday afternoon, broadcaster NRK reported.
“It’s a disaster,” Prime Minister Erna Solberg told reporters after visiting the site.
“There might be people trapped… but at the same time, we can’t be sure because it’s New Years Eve, which means people might be somewhere else,” she said, adding that rescue operations could take a long time.
“The situation is still so volatile that it is impossible to make any (rescue) effort other than helicopters.”
In a tweet on Wednesday, she wrote: “It hurts to see how the forces of nature have ravaged Gjerdrum.”
Helicopters continued to hover over the area after dark, sometimes lowering rescuers towards the debris of collapsed houses. Police said rescue operations would continue from Wednesday evening to Thursday.
Residents spoke about their experience.
“There were two massive tremors that lasted a long time and I assumed it was snow being plowed or something,” Oeystein Gjerdrum, 68, told NRK.
“Then the power suddenly went out, and a neighbor came to the door and said we had to evacuate, so I woke up my three grandchildren and told them to get dressed quickly.
Masses of land are still moving in what was one of the biggest clay slides in recent Norwegian history, said Toril Hofshagen, regional head of the Norwegian Directorate for Water Resources and energy, at a press conference.
Southern Norway has experienced large amounts of rainfall in recent days, which may have resulted in a displacement of the clay soil prevailing in the region, broadcaster NRK said.