How to configure openoffice to properly open UTF-8 *.xls file with html table?

Question

I have HTML document which is written with c#(asp.net) as HTML table in UTF-8 encoding into *.xls file. This is done with purpose, that MS Excel and OpenOffice opens it as sheet, not as plain text.

Content example:

<table>
    <tr>
        <td>
            some UTF-8 text
        </td>
    </tr>
</table

So currently, I'v managed to write content in UTF-8, so MS Office on Windows and Mac opens this *.xls file properly, BUT OpenOffice on Mac doesn't opens this file well, meaning that I see some strange symbols, but not my text.

The question is: what I should do that OpenOffice understood the encoding of the file?

P.S. I didn't had time to test OpenOffice on Windows yet.