Cant remove objects using Three.JS

I'm using Three.JS to make a plane and put some boxes over it I need remove all boxes sometimes. So I'm trying to do it with the following code:

for ( i = 0; i < scene.children.length; i ++ ) {
    var object = scene.children[ i ];
    if ( object != plane && object != camera) {
        scene.remove(object);
    }
}

/This kill each object that is not the plane or the camera ;-)/

It deletes some boxes, but not all of them =( How can I delete all boxes? Greetings, José