At least six people are dead after a large chunk of an Alpine glacier broke loose and sparked an avalanche on a popular trail, authorities have said.
Nine were injured in the incident, said Civil Protection official Gianpaolo Bottacin, as he issued a warning that the number could increase.
Mr Bottacin told Italian news agency Ansa that the situation was “evolving” and there could be up to 15 people missing.
Rescuers were checking licence plates in the car park to determine how many people might be unaccounted for. The process was expected to take hours, national Alpine rescue corps spokesman Walter Milan told AP.
Late in the evening, the corps tweeted a phone number for family or friends to call in case of “failure to return from possible excursions” to the glacier.
The glacier, in the Marmolada range, is the largest in the Dolomite mountains in north-eastern Italy. It has been rapidly melting away in recent years.
Experts at Italy’s state-run CNR research centre, which has a polar sciences institute, said the glacier would no longer exist in the next 25 to 30 years as much of its volume was already gone.
The Mediterranean basin, shared by southern Europe, the Middle East and northern Africa, has been identified by UN experts as a “climate change hot spot” that is expected to suffer heatwaves and water shortages, among other consequences.
“We saw dead [people] and enormous chunks of ice, rock,” rescuer Luigi Felicetti told Italian state TV.
There were no details immediately available on the nationalities or ages of the dead, Mr Milan said. Of the survivors in hospital, two were in grave condition, authorities said.
The fast-moving avalanche “came down with a roar the could be heard at great distance”, local online media site Ildolomiti said.
The search for victims was halted for the night to assess the risk of more chunks of ice breaking off from the glacier, rescuer Walter Cainelli told state television.
Rescuers said blocks of ice continued to tumble down. A light rain began to fall in the early evening.
The SUEM dispatch service, which is based in the nearby Veneto region, said 18 people who were above the area where the chunk of ice struck would be evacuated by the Alpine rescue corps.
Some of those making the trek in the area where the avalanche barrelled through were tied together by rope, according to local emergency services.
Mr Milan said some of the hikers might be able to come down by themselves or use the peak’s cable car.
The SUEM said the avalanche consisted of a “pouring down of snow, ice and rock”. The detached section is know as a serac, or a pinnacle of ice.
Called the “queen of the Dolomites”, Marmolada is about 3,300 metres high and the tallest of the 18 peaks in that eastern range of the Italian Alps, offering spectacular views of other Alpine peaks.
The Alpine rescue service said in a tweet that the segment broke off near Punta Rocca, or Rock Point, “along the itinerary normally used to reach the peak”.
It was not known what caused the section of ice to break away and rush down the peak’s slope, but an intense heatwave which has gripped Italy since late June was thought to be a possible factor.
“The temperatures of these days clearly had influence” on the glacier’s partial collapse, Maurizio Fugatti, president of Trento Province, which borders Marmolada, told Sky TG24 news.
However, Mr Milan said the high heat, which rose unusually above 10ºC on Marmolada’s peak in recent days, was only one possible factor in Sunday’s tragedy.
“There are so many factors that could be involved,” Mr Milan said. Avalanches, in general, are not predictable, he said, and the heat’s influence on a glacier “is even more impossible to predict”.
The injured were flown to several hospitals in the regions of Trentino-Alto Adige and Veneto, according to rescue services.
As with other cases of disasters in Italy, prosecutors opened an investigation to see if there was any indication of possible wrongdoing linked to the avalanche.