ActionScript 3.0 :: Flash MovieClip Still Exists Without Being Displayed?

I add a movie clip on a displayobject like this : (mc is a MovieClip with frames on it)

Code:
mc = new Mc();
levels.addChild(mc);

So here it is, my mc is displayed on levels object..For debug reason at each frame in my mc object i use :

Code:
trace("mcMoves on "+parent )
//it traces "mcMoves on [object Levels]"

Now i want to remove it (and all the objects displayed on the level object) like this:

Code:
while (levels.numChildren) levels.removeChildAt(0);
levels = null;

So everything disappears, but it still trace :

"mcMoves on null"

so my object just disappear from my view, not from the code, how can i erase my object for good ?