[Orgmode] Tables and Images are shifted to the end of document while exporting to tex file

[Keith]

Dear all,

I have a document containing total around 10 images and tables with the 
attribute setting "#+ATTR_LaTex: placement=[htb]". However, I notice 
that two of this images and tables are placed in the end of the pdf 
document where shouldn't be their place. At the beginning I thought it 
might be the floating mechanism in Tex system. Nevertheless, after 
trying lots of tuning in vain, I noticed the position of these image and 
table were shifted to the end of the file just before "\end{document}" 
and this causes the mistake of the position.

Does anyone has idea about it?

Keith