N-tv television and the Bild newspaper said the accidentoccurred in snowy weather on Thursday morning when around 400 federal police officers were conducting a training exercise on dealing with football violence.
Footage on n-tv showed at least one helicopter on its side on the ground.
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The devices cause dogs to yelp, squeal, crouch and exhibit physiological signs of distress.
A frost-free night for most but chillier than previous nights.