I watched an episode of X-Files last night (called "E.B.E.") that included the proverbial swamp gas explanation, amongst others. Very timely.
Now, with all this attention you've drawn to yourself, listen out for strange clicks and hisses on your phone line, and plain-looking cars, that you've never seen before, parked on your street. Oh, and a tradesman who "needs to check your gas connection" but who strangely looks very clean, quiet and observant may not be who he seems to be.