An avalanche in the French Alps swept seven climbers to their deaths on Tuesday and injured one other, the prefect of the Hautes-Alpes region said, raising the initial death toll.

The bodies of at least two missing climbers had been found, said Pierre Besnard, the ranking state official in the region.

The victims included at least two nationalities, Besnard told BFM television. He didn't name the countries. The bodies were being taken to the town of Briancon.

The avalanche hit three groups climbing on ropes on the highly traveled dome of the Ecrins massif, which reaches 13,000 feet, near the town of Pelvoux. Top-level climbing skills aren't needed. However, Col. Christian Flagella told iTele TV station that the area can become "relatively dangerous" under certain conditions.

The guardian of a nearby refuge alerted authorities to the avalanche, the prefect said.

Rescue teams were reinforced. Interior Minister Bernard Cazeneuve said three helicopters had been mobilized, along with two teams of search dogs. The rescue teams were scouring the area to ensure they had found all the victims.