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.
More top news
The social network has had to refine its policy on real names, saying users should use 'authentic' but not necessarily their legal names.
One estimate suggests that higher mortgage repayments could squeeze hard-pressed householders into debt peril.
Calculate your monthly mortgage repayments if interest rates rise.