By Marta Nogueira and Jeb Blount RIO DE JANEIRO (Reuters) - Brazilian prosecutors charged 21 people with qualified homicide on Thursday for their roles in the collapse of a tailings dam at the Samarco Mineração SA iron ore mine last November that killed 19 people. The charges follow what is now considered to be the largest environmental disaster in Brazil's history. Samarco, its co-owners Vale SA and BHP Billiton Ltd, and Brazilian engineering company VOGBR Recursos Hidricos e Geotecnica Ltd which certified the dam's safety, were charged with environmental crimes.
