Hopes of finding eight people missing after a massive landslide in the Swiss Alps alive are fading, police said Friday, as a fresh barrage of sludge forced more evacuations.

Just as some residents on Friday afternoon were gingerly returning to their homes in Bondo, a village near the Italian border hit by a giant landslide on Wednesday, a new river of mud flooded down the mountainside.

"The people who had returned to their homes were temporarily evacuated," regional Graubunden police said in a statement.

Around 100 people were evacuated from Bondo and two Alpine cabins Wednesday amid fears of fresh landslides, and police only gave the green light around midday Friday for some to return home.

An AFP photographer who had been shooting images of the devastation wreaked by the initial landslide said he "suddenly saw a cloud of smoke rise from the mountain."

"Minutes later I saw a river of mud descend on the village," he said, adding that houses that previously had a thick layer of mud around their foundation were now all but engulfed by the grey mass.

The addition sludge will likely complicate further the massive search and rescue mission underway for eight hikers, from Germany, Austria and Switzerland, who have been missing since Wednesday's landslide.

- Hope dwindling for missing -

Police said they had set off in separate groups in the Val Bondasca region where the landslide occurred, apparently ignoring signs recently posted in the village warning of the danger of falling rocks in the area.

Some 120 emergency workers equipped with infrared cameras and mobile phone detectors, helicopters and rescue dogs have been scouring a five-square-kilometre (1.9-square-mile) area.

Police and residents stressed mobile phone coverage in the area was spotty, voicing hope it could explain why those still missing had not been in touch.

But authorities acknowledged that the likelihood of a happy ending was dwindling fast.

"The chances of survival are not high," local police spokesman Roman Ruegg told reporters Friday.

Swiss President Doris Leuthard, who examined the site from the air on Thursday, said the probability that the hikers were dead "is increasing by the hour," Blick reported.

Dramatic footage from Wednesday showed an entire mountainside disintegrating, unleashing an unstoppable mass of thick mud and sludge that tore up trees and demolished at least one building in its path.

Police said 12 farm buildings, including barns and stables, had been destroyed in the initial landslide, while the Graubunden canton's main southern highway was closed to traffic.

- Deafening bang -

"It was terrible," Elisa Nunzi told Blick after witnessing the landslide from her home in a higher-altitude village.

The 27-year-old said she heard a deafening bang that sent rocks pouring down the mountain. "There were so many. It did not stop."

Christian Speck, manager of a hotel in Soglio, several kilometres (miles) from Bondo, also witnessed the mountainside collapsing.

"At breakfast time, my customers and I saw rocks come lose from the mountainside and slide towards Bondo, in a huge cloud of smoke," he told AFP.

The landslide set four million cubic metres (141 million cubic feet) of mud and debris in motion, its relentless mass stretching 500 metres (1,600 feet) across, according to the regional natural hazards office (AWN).

The event was so severe that the vibrations set off seismometers across Switzerland, measuring the equivalent of a 3.0 magnitude earthquake, according to the Swiss Seismological Service.

Experts hinted that climate change could be partially to blame for the disaster, with melting permafrost and an adjacent glacier likely destabilising the landmass.

Source: AFP