MINNEAPOLIS (AP) - The sight of low-flying helicopters weaving through buildings in downtown Minneapolis and St. Paul had some people on edge.

But, police say the swarm of choppers is only a training exercise that will be conducted for several nights this week.

Some residents say they saw as many as seven helicopters flying in formation in the night sky Monday.

Twitter buzzed with concerned comments about the choppers.

Police say the training is a Department of Defense exercise.

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