At least six people have died after a large chunk of alpine glacier broke loose and slid down a mountainside in Italy. The collapse on Sunday afternoon sent ice, snow and rock slamming into hikers on a popular trail on the Marmolada peak, killing at least six and injuring eight, authorities said. Gianpaolo Bottacin, a local civil protection official, said the situation was “evolving” and that there could be perhaps 15 people missing. In late evening, the National Alpine and Cave Rescue Corps tweeted a phone number to call for family or friends in case of “failure to return from possible excursions” to the glacier. Rescuers were checking number plates in the car park as part of checks to determine how many people might be unaccounted for, a process that could take hours, said Walter Milan, a spokesman for the Corps. It had earlier tweeted that the ongoing search of the peak involved rescue dogs and at least five helicopters, but the operation was paused on Sunday night amid fears that more of the glacier could come away. The rescue corps had said the hikers were “hit by the detachment of the serac”, using a term for a pinnacle of a glacier. “There are eight injured, two of them in grave condition.” The SUEM (Servizio Urgenza Emergenza Medica) dispatch service, based in the nearby Veneto region, said 18 people who were above the area where the ice struck would be evacuated by the rescue corps. The dispatch service said the avalanche consisted of a “pouring down of snow, ice and rock”. Marmolada, which is about 3,300 metres (11,000ft) high, is the tallest peak in the eastern Dolomites. “A breaking away of rock provoked the opening of a crevasse on the glacier, leaving about 15 people involved,” the emergency dispatchers tweeted. 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 was not immediately clear what caused the section of ice to break away but the intense heatwave that has gripped Italy since late June could be a factor, said Milan. “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.” The injured were flown to several hospitals in the regions of Trentino-Alto Adige and Veneto, according to rescue services.