SÃO PAULO, Brazil — As an American investment giant that manages the retirement savings of millions of university administrators, public school teachers and others, TIAA-CREF prides itself on upholding socially responsible values, even celebrating its role in drafting United Nations principles for buying farmland that promote transparency, environmental sustainability and respect for land rights.

But documents show that TIAA-CREF’s forays into the Brazilian agricultural frontier may have gone in another direction.

The American financial giant and its Brazilian partners have plowed hundreds of millions of dollars into farmland deals in the cerrado, a huge region on the edge of the Amazon rain forest where wooded savannas are being razed to make way for agricultural expansion, fueling environmental concerns.

In a labyrinthine endeavor, the American financial group and its partners amassed vast new holdings of farmland despite a move by Brazil’s government in 2010 to effectively ban such large-scale deals by foreigners.