A small number of people are believed to be injured and more are stranded on chairlifts after the incident, which happened around 3.25pm.
There are no details on the extent of injuries as yet, but the focus is currently on evacuating those injured and rescuing those who remain on the chairlift.
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The cyclist said the victory was as sweet as his first win as he became the first Briton to win the race three times.
Local police confirmed the explosion, which occurred near Nuremberg.
Temperatures slide a couple of degrees