|A collapse of the Trift glacier in the Swiss Alps could trigger an ice avalanche|
Hundreds of people have been forced to evacuate in the south of Switzerland because of the risk of a glacial ice avalanche.
The authorities believe warm weather has made the alpine Trift glacier unstable.
Geologists monitoring the ice recently noticed it was shifting by as much as 50in (130cm) in a single day.
"A large serac could collapse at any moment," said the police in the canton of Valais, referring to a the pinnacle or ridge of ice on the surface of a glacier.
A glacial collapse could trigger an ice avalanche that may reach the popular resort of Saas-Grund, dubbed the "Hiking Pearl".
Police spokesman Simon Bumann said that 222 people have been evacuated.
The area below the glacier and hiking paths in the area have been closed off, while mountain lifts and a local road have also been shut.
The glacier has been under observation since October 2014, when the area was closed for three weeks.
The ban was lifted as colder temperatures returned, but increased movement on the lowest part of the glacier in recent days has prompted the return of restrictions.
Radar surveillance has been put in place to monitor the glacier.
An avalanche in August buried eight hikers after being triggered by a massive rockfall in another valley in the Swiss Alps, near Bondo.