Hola Paul, I hope this works for you.

Depende del contexto...
Trata de blancas = human trafficking (prostitution)
Trafico de inmigrantes = human trafficking (normally illegal immigrants)

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Note added at 22 mins (2005-05-04 15:41:07 GMT)
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España y Marruecos intensificarán su colaboración en materia de inmigración en particular para luchar contra las redes de tráfico de inmigrantes ilegales informó el martes el ministerio del Interiores.news.yahoo.com/050126/159/3vhw8.html

Sábado 4 de Diciembre de 2004 - 12:29 hs. Proponen asistir a víctimas de la \"trata de blancas\" Pablo Hulet. El legislador renovador solicitó que se asista a víctimas de la \"trata de blancas\". ... atención y acompañamiento de las personas que han sido víctimas de la \"trata de blancas\". El diputado reseñó que ...ww.territoriodigital.com/nota.aspx?c=9832356427820417 - 12k - Cached - More from this site


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Note added at 15 hrs 41 mins (2005-05-05 06:59:09 GMT)
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He visto varios artículos en la web y todos se refieren a lo mismo: Prostitución y trata de blancas.

http://www.deshkapoor.org/archives/2005/04/_human_traffick.h...
Asia is a particularly burgeoning market where sex trafficking is concerned. Women are especially victimized in poor countries like Nepal where they have low status and limited employment opportunities. UN agencies estimate that some 200,000 Nepalese women and girls are in sex brothels in India, for example. While there are heated debates over what constitutes voluntary vs. involuntary prostitution, it remains that thousands of women and girls are forced into this business. Countries like Thailand, Cambodia, and Bangladesh are also at the center of the sex trafficking trade.