How to reach css and image files from the html page loaded by javafx.scene.web.WebEngine#loadContent?

Question

I have a String HTML content which is loaded into webEngine by loadContent() method. I have also some css and image files used in this page. Although I put these file into the same package of java class, the loaded page cannot find them. Looked for API docs and web, but could not find any appropiate similar solutions. How I load these files?