Swiss authorities have evacuated hundreds of people in the alpine glacier area of Trift in the country's south, warning of a possible glacial ice avalanche.
"A large serac could collapse at any moment," the police in the canton of Valais said in a statement. A serac is a pinnacle or ridge of ice on the surface of a glacier.
Geologists have recently noticed significant movement along the "tongue" of the Trift glacier, most recently up to 130 centimetres (50 inches) in a single day, local authorities said.
A collapse would threaten the municipality of Saad-Grund. Authorities have already evacuated 222 people, a police spokesman Simon Bumann told AFP.
A glacial collapse could trigger an ice avalanche which could reach the village.
The area directly below the glacier and hiking trails in the region has been closed, while lifts and a local road have been sealed off.
The glacier has been under observation since October 2014, when the area was closed for three weeks. With a return to colder temperatures, the situation stabilised and the access ban was lifted.
But since the start of the week, movement has increased on the lower part of the glacier. Radar surveillance has been put in place.
In late August, a massive rockfall triggered an avalanche which buried eight hikers in another valley in the Swiss alps, near Bondo.