Rescuers used thermal drones on Monday to search for possible survivors of glacier collapse on Marmolada, the highest mountain in the Italian Dolomites.
At least six people were killed on Sunday when a glacier ruptured and slid down the mountainside. Nine injured survivors were found and flown by helicopters to hospitals in northeastern Italy.
It still unclear how many people might have been hiking on the Marmolada peak and are unaccounted for. Sixteen cars remained unclaimed in the area's parking lot.
Trento Prosecutor Sandro Raimondi said that 17 hikers were believed to be missing. However, authorities also warned that the chances of surviving in such conditions for a long period of time were very bleak.
Chances of finding more survivors "are slim to nothing," the region's Alpine Rescue Service head Giorgio Gajer told AGI news agency.
Two Germans injured in the accident
Four victims were identified on Monday, three of them Italian, including two alpine guides, and another from the Czech Republic, news agency AGI reported, citing rescuers.
The German Foreign Ministry told the dpa news agency that it was working on the assumption that two Germans were injured in the accident. Health authorities in Belluno said later on Monday that two rescued Germans were being treated in hospital, a 67-year-old man and a 58-year-old woman.
Italian Premier Mario Draghi and the head of the national Civil Protection agency were expected to go on Monday to Canazei, a tourist town in the Dolomite range which has been serving as a base for rescuers.
Relatives were also expected to go to the town to identify bodies when rescuers can safely remove them from the mountain.
Record-high temperature at summit
What caused a pinnacle of the glacier to break off and thunder down the slope, was not immediately known. But the heat wave, bringing unusually high temperatures for the start of the summer at high altitude in the Alps, was being cited as a very likely factor.
The disaster struck one day after a record-high temperature of 10 degrees Celsius (50 Fahrenheit) was recorded at the summit of Italy's largest glacier.
According to Massimo Frezzotti, a science professor at Roma Tre University, the collapse was caused by unusually warm weather linked to global warming, with precipitation down 40 to 50 percent during a dry winter.
Jacopo Gabrieli, a polar sciences researcher at Italy's state-run National Research Council (CNR), noted that the long heat wave, spanning May and June, was the hottest in northern Italy in that period for nearly 20 years.
"The current conditions of the glacier correspond to mid-August, not early July," Gabrieli said.
The glacier, in the Marmolada range, is the largest in the Dolomite mountains in northeastern Italy. It has been rapidly melting away over the past decades, with much of its volume gone. Experts at CNR estimated a couple of years ago that the glacier was likely to disappear within 25-30 years.
dh/msh (AP, dpa, AFP, Reuters)