Rescue workers and sniffer dogs are being deployed and staff at the sprawling resort are being mobilised, a journalist said at the scene.
"According to witnesses there are many people under the avalanche," a police spokesman said.
Five French Foreign Legionnaires killed in Alps avalanche
Poor visibility is so far preventing the deployment of helicopters.
The avalanche hit at about 10:00 am (0900 GMT).
Tuesday's avalanche risk – normally assessed only for off-piste and closed slopes – was at four on a scale of five.
At level five, all slopes are closed.
An avalanche killed four people who were exploring an off-piste section in the same area on February 13.
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