Positive drug test

If I am drug tested by the police through my workplace, and I test positive for thc, could the police charge me? My workplace doesn’t care, I’m a very occasional smoker and don’t possess my own weed, but expect I may be tested due to a recent event (not involving me or weed) and would like to know if I need to avoid partaking in smoking until it all blows over. Could testing positive prove possession even if I was smoking someone else’s weed?

Thank you! Sorry for the rather vague details.