How to hide or delete movieclip using AS3

I have different layers and different movieclip in the stage and when the movieClip is clicked it load the external movieclip.

here is the code

var swfLoader:Loader;

function swfLoaded(evt:Event):void

{

var myStates:MovieClip = (evt.target.content) as MovieClip;

addChild(myStates);

}

function loadLondon(evt:MouseEvent):void

{

swfLoader = new Loader();

swfLoader.contentLoaderInfo.addEventListener(Event.COMPLETE ,swfLoaded);

swfLoader.load(new URLRequest("london.swf"));

}

london.addEventListener(MouseEvent.CLICK, loadLondon);

Here external SWF is loaded sucessfully fully but  all the content remain in back.( I mean i can see the london and other behind the new swf);

how to remove those contents(ie. london );

I mean when i load external swf all the elements in current state must me removed and i can only see the new swf in the stage.

Please Help me