How to add an existing Xml string into a XElement

How to add an existing Xml string into a XElement?

This code

        var doc = new XDocument(
            new XElement("results", "<result>...</result>")
        );

of course produces this

  <results>&lt;result&gt;&lt;/result&gt;</results>

but I need this

  <results><result>...</result></results>

Any ideas?