By Stan Bush

WHEAT RIDGE, Colo. (CBS4)– Wheat Ridge police say they have a true mystery on their hands.

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Investigators in the Denver suburb have received dozens of reports of a loud “boom” happening overnight.

Neighbors have said the noise, which some describe as an explosion or a gunshot, only happens once around 3 a.m. typically over the weekend. The noise, according to reports, only happens once, but has been occurring for months now.

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“I was dead asleep and ‘What was that?’ and then I’m back asleep. Now it seems like even more of a mystery,” says Sara Anthony of Wheat Ridge. “You can hear it a ways away, but it’s loud enough to wake me up.”

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Police say they do not know where the noise is coming from. Witnesses have reported it online, but have not called 911 when it happens, so there is not a good record of when it occurs.

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The noise, some speculate, could be a malfunctioning electrical transformer, or a homeowner firing a gun. Some neighbors say they worry the noise is something not so easily explained.

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Stan Bush is a general assignment reporter at CBS4. His stories can be seen on CBS4 News at 10. Read his bio and follow him on Twitter @StanBushTV.