Accused Of Drinking At Work.

So I work at a dispensary in Colorado it is illegal to have alcohol on the grounds whatsoever. I received a phone call from HR that apparently I've been reported by multiple people for drinking straight vodka from a water bottle. One which is impossible because the water bottle I use doesn't ever leave the building in a refill it from their deep rock water fountain and keep it in the fridge And as everybody knows everything is on camera at the dispensaries. So I guess my question is what do I do now that these accusations have been made and they won't even tell me who made these accusations or exactly what these accusations were other than I was drinking vodka on the job. So I guess my question is what do I do now