I'm using map module to redirect URLs which have been removed (but indexed by search engine).
But how can I fall back to http 404 response for urls not present in my redirect list?

I've tried following, but I got 200 instead of 404:

location ~* ^/404$ {
return 404;
}

error_page 404 = /404.html;

map $uri $redirected_uri {
default /404; #here?
include /etc/nginx/redirected_uri.txt;
}

location ~* ^/.+ {
if (!-f $request_filename) {
rewrite ^ $redirected_uri permanent;
}
}