Authorities said conditions in the Italian Alps were too unstable Wednesday for search teams and dogs to work on the mountain where five people remained missing after a fatal weekend avalanche.
Seven people were killed after an enormous chunk of a glacier broke off Sunday, sending an avalanche of ice and rocks thundering across a trail where hikers were enjoying warm, sunny weather.
Rescuers said they hoped the temperature would dip Thursday, lessening the risk of more avalanches, so searchers could go on the Marmolada slope.
Relatives of the missing Italians pressed for the retrieval of their loved ones' bodies, which are believed to be buried under the avalanche. The size of the glacier's detached pinnacle has been compared to an apartment building.
Trento Prosecutor Sandro Raimondi said in a Wednesday interview on Italian state radio that he opened a formal investigation to determine if any negligence was involved. Prosecutors plan to consult geologists.
But Raimondi said it appeared at this point that the avalanche couldn't have been anticipated.
"The unpredictability in this moment is the chief protagonist,'' he said.
Forensic police investigators dispatched from the city of Parma took samples Wednesday from some of the remains recovered to try to determine if they belonged to any of the people missing.
Meanwhile, the mayors of Canazei and smaller towns at the base of mountains in the Dolomite range issued ordinances closing off the Marmolada peak to hikers. Some people ignored the orders and scrambled up the lower slopes.
Authorities have cited a weeks-long heat wave in northern Italy and scant winter snowfall as likely factors in the weekend breakup of the glacier, which has dramatically shrank over decades.
Last weekend, the temperature on Marmolada topped 10 degrees Celsius (50 F), unusually high for early summer, authorities said.
Polar sciences experts at an Italian government-run research center estimated that the Marmolada glacier could disappear entirely in the next 25-30 years if current climatic trends continue.
Between 2004 and 2015, the glacier lost 30% of its volume and 22% of its area.
People whose livelihoods are entwined with the mountain offered their own observations. Carlo Budel, manager of alpine hut on the side of Marmolada, recalled that the glacier was not covered with snow last month.
"Last year, when I moved to the hut on June 1st, it took me half a day only to enter because the hut was all covered in snow,” he said. “But this year, I opened the main door in just 30 minutes.”
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Andrea Rosa and Paolo Santalucia contributed to this report.
