A large chunk of Alpine glacier broke loose and roared down a mountainside in Italy, sending ice, snow and rock slamming into hikers on a popular trail on the peak and killing at least six and injuring eight, authorities said.
It couldn't immediately be determined how many hikers were in the area or whether any were missing, said Walter Milan, a spokesperson for the national Alpine rescue corps, who provided the death and injury toll.
Rescuers were checking licence plates in the parking lot as part of checks to determine how many people might be unaccounted for, a process that could take hours, Milan said.
"We saw dead [people] and enormous chunks of ice, rock," exhausted-looking rescuer Luigi Felicetti told Italian state TV.
Nationalities or ages of the dead weren't immediately available, Milan said. Of the eight hospitalised survivors, two were in grave condition, emergency dispatch services said.
The fast-moving avalanche "came down with a roar and could be heard at a great distance", local online media site ildolomiti.it reported.
Earlier, the National Alpine and Cave Rescue Corps tweeted that the search of the involved area of Marmolada peak involved at least five helicopters and rescue dogs.
The SUEM dispatch service, which is based in the nearby Veneto region, said 18 people who were above the area where the ice struck would be evacuated by the Alpine rescue corps.
But Milan said some on the slope might be able to get down by themselves, including by using the peak's cable car.
SUEM said the avalanche consisted of a "pouring down of snow, ice and rock". The detached section is known as a serrac, or pinnacle of ice.
Marmolada, towering about 3300m, is the highest peak in the eastern Dolomites, offering spectacular views of other Alpine peaks.
The Alpine rescue service said in a tweet that the segment broke off near Punta Rocca (Rock Point), "along the itinerary normally used to reach the peak".
It wasn't immediately clear what caused the section of ice to break away and rush down the peak's slope. But the intense heat wave gripping Italy since late June could be a factor.
"The temperatures of these days clearly had influence" on the glacier's partial collapse, Maurizio Fugatti, the president of Trento Province, which borders Marmolada, told Sky TG24 news.
But Milan stressed that high heat, which soared unusually above 10C 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," Milan said. Avalanches in general aren't predictable, he said, and heat's influence on a glacier "is even more impossible to predict".
In separate comments to Italian state television, Milan called the recent temperatures "extreme heat" for the peak. "Clearly it's something abnormal."
The injured were flown to several hospitals in the regions of Trentino-Alto Adige and Veneto, according to rescue services.