Problem Closing Forms

I created the main search screen form SearchScrn (fsNormal) with the ability to create as many new forms on the fly (they are not children of MDI form) as possible after a search is refined. I can close all of these forms using one button click event:

procedure TSearchScrn.CloseAllBtnClick(Sender: TObject);
begin
SearchScrn.Close;
end;  { TSearchScrn.CloseAllBtnClick }

This works, but if I want to start new search, I try to close all forms and create a new main SearchScrn form:

procedure TSearchScrn.SearchListBtnClick(Sender: TObject);
var
  SearchStr1     : String[20];
  SearchOp       : String[ 3];
  SearchStr2     : String[20];
begin
  if Pos('New',SearchListBtn.Caption)>0 then
     begin
     SearchStr1:=SearchFld.AsString;
     SearchOp  :=SearchOperator.Text;
     SearchStr2:=SearchFld2.AsString;
     SearchScrn.Close;
     SearchScrn := TSearchScrn.Create( Self );
     with SearchScrn do
          begin
          SearchFld.AsString:=SearchStr1;
          SearchOperator.Text:=SearchOp;
          SearchFld2.AsString:=SearchStr2;
          MakeSearch;
          ShowModal;
          end;
     end
     else
       MakeSearch;
end;  { TSearchScrn.SearchBtnClick }

For some reason SearchScrn.Close does not close all the forms and instead leaves them on the screen.

Answer:
One thing that you should do is to 'Free' the form after closing it. Also, to make doubly sure that the form variable's reference is gone, set it to 'nil' after freeing it.