How to delete tag in search result page

I want to write a plugin, to customize search result page.
I deleted some entities using :
    elgg_unregister_entity_type('object', 'xxx');
It worked properly.

Now, I don't know, how to delete "Commets" (ie, search_type=comments) and "Tags" (ie, search_type=tags) there. 
So, how to do that?