A significant portion of an alpine glacier in Italy broke free and crashed down a mountainside, killing at least six people.

At least six people were killed and eight others were hurt when a section of a popular hiking trail on the Marmolada peak collapsed on Sunday afternoon.

Local civil protection official Gianpaolo Bottacin stated that the situation was "evolving" and that there may be as many as 15 individuals missing.

A phone number to call for relatives or friends in the event of "failure to return from possible excursions" to the glacier was tweeted by the National Alpine and Cave Rescue Corps in the late evening.

According to Walter Milan, a spokesperson for the Corps, rescuers were looking at license plates in the parking lot as part of checks to see how many individuals might be missing. The process might take hours.

It had earlier tweeted that rescue dogs and at least five helicopters were employed in the mountain's continuous search. Still, on Sunday night the operation was halted due to concerns that an additional glacier may be eroding.

The rescue team had used the term "hit by the separation of the serac"-a glacier pinnacle-to describe how the trekkers had been struck. "There are eight injured, two of them in grave condition."

The dispatch service said the avalanche consisted of a "pouring down of snow, ice, and rock".

The tallest mountain in the eastern Dolomites is Marmolada, which rises to a height of around 3,300 meters (11,000 feet).

"A breaking away of rock provoked the opening of a crevasse on the glacier, leaving about 15 people involved," tweeted by the emergency dispatchers.

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".

The extreme weather that has plagued Italy since late June could be a factor, according to Milan, although it was not immediately obvious what caused the piece of ice to break away.

"The heat is unusual," Milan said, noting that temperatures in recent days on the peak had topped 10C (50F). "That's extreme heat" for the peak, he said. "Clearly it's something abnormal."

According to the rescue services, the injured were transported to a number of hospitals in the Trentino-Alto Adige and Veneto regions. The dead's nationalities or ages weren't immediately known, according to Milan. Authorities reported that two of the hospitalized survivors were in critical condition.