PARIS -- French authorities say four skiers have been killed, one is injured and another is missing after an avalanche in the southern Alps.

The French gendarmerie said the avalanche happened Friday in Entraunes, near the Italian border. The cause of the avalanche is unknown.

During a visit to the southern city of Nice, Prime Minister Edouard Philippe told reporters that rescue operations are still ongoing.

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Local media said the skiers, including a guide, were off-trail in a remote area of the Mercantour national park.

French authorities had warned against a high risk of avalanche in the Alps following heavy snowfall in recent days.