ROME, Italy (AP) — Some 17 people remain unaccounted for a day after a huge chunk of an Alpine glacier broke off and slammed into hikers in northern Italy, officials said Monday.

At least six people died and 9 were injured by the avalanche of ice, snow and large rocks thundering down the slope of the mountain topped by the Marmolada glacier Sunday afternoon.

Trento Prosecutor Sandro Raimondi said that 17 hikers were believed to be missing, the Italian news agency LaPresse reported.

Veneto regional Governor Luca Zaia said some of those hiking in the area on Sunday, were roped together as they climbed.

Nationalities of the known dead haven’t been disclosed, and conditions were too dangerous Monday morning for rescue crews with dogs to resume the search for those missing or to bring down the bodies.

The bodies will be brought to an ice skating rink in the resort town of Canazei in the Dolomite mountain range for identification.

Raimondi was quoted as saying two of the nine injured are Germans. Zaia told reporters that one of the Germans was a 65-year-old man. Of the injured patients, one of those in intensive care has yet to be identified.

The patients suffered chest and cranial injuries, said Zaia.

Drones were being used to look for any of the missing as well as verify safety.

Sixteen cars remained unclaimed in the area’s parking lot, and authorities sought to track down occupants through license plates. It was unclear how many of the cars might have belonged to the already identified victims or to the injured, all of whom were flown by helicopters on Sunday to hospitals.

What caused a pinnacle of the glacier to break off and thunder down the slope at a speed estimated by experts at some 300 kph (nearly 200 mph), wasn’t immediately known. But the heat wave gripping Italy since May, bringing temperatures unusually high for the start of summer even up in the normally cooler Alps was being cited as a likely factor.