Broken encoding in Excel report from Java

in my application user is able to download an excel report. When user downloads xls using FF then encoding is fine and umlauts are shown correct. If user does the same in IE and Chrome then umlauts in xls are broken.

Excel report is generated in a servlet using Apache POI v3.10.1 and filled with the same data every time. But the xls files downloaded in FF and IE (or Chrome) are different.

Any idea why?

BTW, I tried to set encoding in response header

response.setHeader("Content-Type", "application/vnd.ms-excel; charset=UTF-8");

but no success.