AURORA, Colo. (CBS) – Anyone driving by the Wells Fargo Bank at Sable and Mississippi in Aurora on Friday morning would have thought some sort of major crime had happened.

There were police cars with flashing lights, bank customers in handcuffs, news crews and frightened faces. The confusing scene in the end turned out to just be a major misunderstanding involving balloons.

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Aurora police dispatchers first received a call of shots fired and a possible robbery in progress at the bank, located at 999 S. Sable Boulevard. More than a dozen officers responded and quickly set up a perimeter.

A Brinks armored car employee and some bank customers told officers they had heard the sound of gunshots.

“We heard gunshots but we didn’t know where they were coming from,” said customer Debra Brassell.

There were other suspicious signs as well.

“A vehicle left, a white Suburban, at a high rate of speed,” Sgt. James Lesansky with Aurora police told CBS4. “Also, when we started setting up we had to gentlemen running out of the building.”

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Police then checked bank customers for weapons, handcuffing them just to be safe.

“During the course of this active police operation, officers determined that in fact no shots had been fired and no robbery had occurred,” said Officer Bob Friel, an Aurora police detective.

The mystery was soon solved when it was determined that the loud popping sounds had just been balloons popping. A holiday party had been going on in the bank.

“It turns out it was three or four helium balloons that were overfilled,” Lesansky said. “They rose to the top and exploded.”

Once it was determined the scene was clear officers said their effort turned out to be good training for future bank robbery scenarios.

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FBI Community Outreach Specialist Dave Joly told CBS4 that in 2010 there were 163 bank robberies in Colorado. Of those, 97 were solved.