Extra junk bytes before outputting Image

Hi All, 

In latest Elgg.(probably 3.0.3) I am seeing that whenever I output image from php code. the browsers gets 1 extra byte prepended to the output.   

For example the captcha plugin is not working. and there also the problem is same. If I remove that extra line from saved file(wget command) then I can see the image.

I verified that there is no new line  in captcha/captcha.php.

I tried ob_clean(). still same issue.