My guess is that it's the police like you said and if that's the case just call them and let them know what's going on.  It's better not to waste anymore of your or their time on this.  If you wait until too long and they end up kicking in your door then the dectective will have to have to "make a case" somehow.  Just keep in mind that although mining isn't illegal trading can be if not using a FINCEN trader.  This isn't something they're likely to care about as long as you identify what you're doing now, but if they kick in the door for no reason and need to bring a charge to avoid a lawsuit then this is an easy one to hang on almost any miner.

The other thing you might consider is to think back who you discussed your mining operations with.  Mining equipment is very expensive and an apartment is a soft target.  In this case I also recommend talking to the police and they'll step up patrols in your neighborhood.

The last thing I would say is I still can't see how people using PG&E are mining at home.  Find a hosting company and send your equipment to them.  Less stress and will cost you less.