how to show string in mhtml format in a webview?

Question

I have a string which contains the contents of a web page in mhtml format.

Now I want to display this web page in a Webview for Android devices:

String str = "..."; // this is the mhtml document
webView.loadData(str,"text/html",null);

But this displays the mhtml markup instead of parsing it.
Any help is greatly appreciated.