'Dancing with the Stars' -- The Nancy Grace Fart Mystery

Nancy Grace definitely cut a rug on "Dancing with the Stars" last night ... but did she also cut the cheese???

Listen closely to the clip of Nancy yakking with Brooke Burke after she waltzed to "Moon River." You'll hear what sounds like a fart escaping from someone. As far as we can tell, there are only three possible culprits.

So we ask ...