Fire service spokesman Sven Gerling said his initial information was that two helicopters had crashed, but he had no further details on the accident.
Federal Police spokesman Frank Brochert confirmed there "was an incident during an exercise" and that emergency crews were on the scene. He had no details about the accident.
More top news
Liverpool edged an epic penalty shootout to beat Middlesbrough and progress to the fourth round of the Capital One Cup.
The world famous musical, which has been running on Broadway since 1997, has broken records earning more than £2.8 billion.
There will be wet weather around tonight with rain drifting from north to south which will lead to scattered showers tomorrow morning.