How to remove 404 pages from sitemap in Yii?

Question

Yii

There are a lot of pages on the sitemap.xml that give 404. It is not clear how they stay there if, according to the idea, they should be deleted themselves if such a page does not exist.
Is it possible to somehow transfer pages to the sitemap without 404? Or as that in a DB to clear those pages which are deleted. I haven’t worked with Yii before, I don’t understand how everything works there and why the sitemap contains pages that are no longer there.