Swiss officials have called off a search for eight people missing after a huge landslide struck near the border with Italy, acknowledging they are likely to be buried under millions of tons of rock.

The small village of Bondo was partly buried on Wednesday under metres of collapsing mountain, and regional police said they were expecting more rock and mudslides in the area.

The missing — all hikers — are two Austrians, four Germans and two Swiss.

"We have done everything we could to search for these eight people," Lieutenant Andrea Mittner of the Grisons canton police told a news conference broadcast on Swiss television.

"We used helicopters, dogs and rescue teams and we still did not find anybody.

"We have to reconcile ourselves to the fact that we will not find anybody."

A geologist flew over the site in a helicopter on Saturday to inspect the mountain. ( Reuters: Arnd Wiegmann )

After police warned about the risk of more slides, a geologist flew over the site in a helicopter early on Saturday to inspect the 3,369-metre Piz Cengalo mountain.

Experts have said melting permafrost due to high temperatures was one likely factor in the disaster, but the impact of changes in the mountain's structure over thousands of years appeared to have played a bigger role.

Police are investigating the circumstances of the tragedy to determine if anybody was at fault.

Bondo community leaders said they had sought to make the area as safe as possible, introducing flood-control improvements following a smaller landslide in 2011 and warnings about the unstable terrain.

"What happened fills us with deep regret, but I think we have done everything humanly possible," mayor Anna Giacometti told state TV in an interview broadcast on Saturday.

Police are investigating to determine if anybody was at fault. ( Reuters: Arnd Wiegmann )

Reuters