I found a table of reference populations that FTDNA used for their Population Finder tool:
http://www.familytreedna.com/faq/answers/default.aspx?faqid=...

I only saw entries for "South Asia" and "Southeast Indian," but not "South Indian." If it's South Asia, I'd bet Tatar might be possible, since the representative populations of that group seem related to the Tatars in some way (Uygur, Hazara, Tu, Xibo).