error in generated sitemap.xml – Google Webmaster Tool and browser check

Hi guys,

I get an error when testing the generated sitemap.xml inside Google Webmaster Tool (see attachment) and also when opening the file inside a browser.

Error in browser:

This page contains the following errors:

error on line 2 at column 6: XML declaration allowed only at the start of the document

Below is a rendering of the page up to the first error.

line 2 in sitemap.xml shows this:

<urlset xmlns:xsi='' xsi:schemaLocation='' xmlns='' >

Thanks for your help.