Rescuers warned Monday that hope of finding survivors was diminishing after an avalanche set off by the collapse of an Italian glacier during a heat wave killed at least six people.

Authorities said they did not know how many climbers were hit when the glacier gave way Sunday on Marmolada, the highest mountain in the Italian Dolomites.

Ice and rock thundered down the slope at 300 kilometres an hour (185 miles per hour), according to Trento province chief Maurizio Fugatti.

On Monday, rescuers armed with thermal drones searched for body heat from potential survivors trapped in ice, though hope was rapidly dwindling.

Chances of finding survivors “are slim to nothing”, the region’s Alpine Rescue Service head Giorgio Gajer told AGI news agency.

“We found bodies torn apart, in a shapeless tide of ice and debris stretching over 1,000 metres (3,280 feet),” Gino Comelli from the Alpine Rescue Service told the Corriere della Sera daily Monday.

A spokesman for the Trento province said people were still being reported missing.

Trento’s chief prosecutor Sandro Raimondi was cited by Corriere della Sera as saying he feared the number of dead “could double if not triple”, based on the number of cars in the carpark.

But Canova urged caution, saying the total number of climbers involved was “not yet known”. Eight people were recovered with injuries.

The disaster struck one day after a record-high temperature of 10C (50F) was recorded at the glacier’s summit.

The glacier had been weakened by decades of global warming, experts said.

READ ALSO: UPDATE: Six dead after glacier collapses in Italian Alps

‘Sea of ice’ and heat beyond normal

Emergency services spokeswoman Michela Canova told AFP an “avalanche of snow, ice and rock” hit an access path at a time when there were several roped parties, “some of whom were swept away”.

The total number of climbers involved was “not yet known”, she said. Helicopters and sniffer dogs were called off as night fell and amid fears the glacier may still be unstable.

But rescuers used drones equipped with thermal cameras to continue the search overnight and early Monday, Canazei mayor Giovanni Bernard told AFP.

“It is difficult for the rescuers in a dangerous situation”, he said. Images of the avalanche filmed from a refuge close by show snow and rock hurtling down the mountain’s slopes.

The footage of the large ice avalanche in Marmolada today in close proximity.

We don't know the author, we will write it in the comments as soon as we will know it.

Indeed an impressive sequence pic.twitter.com/zDo4q40qOP

— Alpine-Adriatic Meteorological Society (@aametsoc) July 3, 2022

“It’s a miracle we’re alive,” Stefano Dal Moro, an engineer who was hiking with his Israeli partner told Corriere della Sera.

“There was a dull noise, then that sea of ice came down. It’s useless to run, you can only pray that it doesn’t come your way.

READ ALSO: Heatwave: Most Italian cities on red alert over scorching temperatures

“We crouched down and hugged each other tightly as the ice passed”. Bodies dug out of the ice and rock were taken to the village of Canazei.

Italian Prime Minister Mario Draghi was expected to visit Canazei later Monday.

Massimo Frezzotti, a science professor at Roma Tre University, told AFP the collapse was caused by unusually warm weather linked to global warming, with precipitation down 40 to 50 percent during a dry winter.

“The current conditions of the glacier correspond to mid-August, not early July,” he said.

Glacier specialist Renato Colucci told AGI that the phenomenon was “bound to repeat itself”, because “for weeks the temperatures at altitude in the Alps have been well beyond normal values”.

The recent warm temperatures had produced a large quantity of water from the melting glacier that accumulated at the bottom of the block of ice and caused it to collapse, he added.

The Trento public prosecutor’s office has opened an investigation to determine the causes of the tragedy.