A huge chunk of a glacier in the Swiss Alps broke off on Wednesday afternoon, causing a deluge of ice, mud and rock to bury part of a mountain village evacuated earlier this month due to the risk of a rock slide, authorities said.

One person is currently missing, said Matthias Ebener, a spokesperson for the local authorities in the canton of Valais.

Drone footage broadcast by Swiss national broadcaster SRF showed a vast plain of mud and soil completely covering part of the village of Blatten, the river running through it and the wooded sides of the surrounding valley.

"An unbelievable amount of material thundered down into the valley," said Ebener.

The rubble of shattered wooden buildings could be seen on the flanks of the huge mass of earth in the drone footage.

Buildings and infrastructure in Blatten, whose roughly 300 inhabitants were evacuated on May 19 after geologists had identified the risk of an imminent avalanche of rock and ice from above, were hit hard by the rock slide, Ebener said.

SRF said houses were destroyed in the village nestled in the Loetschental valley in southern Switzerland.

Swiss authorities have been monitoring the slopes above Blatten since ordering residents to leave their homes.

A video shared widely on social media showed the dramatic moment when the glacier partially collapsed, creating a huge cloud that covered part of the mountain as rock and debris came rumbling down into the outskirts of the village.