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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It was a cloudy start across many eastern areas first thing. However, Sunday shaping up to be a warm sunny day for most.
Former Work and Pensions Secretary Iain Duncan Smith has David Cameron should remain prime minister even if Britain votes to leave the EU.
Tony Blair has said Leave campaigners are focusing on immigration "because they've lost comprehensively the debate on the economy".