SAO PAULO May 5 (Reuters) - Shares of Brazil's largest non-government bank, Itau Unibanco Holding SA now carry the heaviest weighting on the benchmark Bovespa stock index, topping state-run oil producer Petroleo Brasileiro SA, exchange operator BM&FBovespa SA said on Monday.
The oil firm known as Petrobras has lost about half of its market value over the past three years, hurt by a government policy that forces it to sell imported fuel at a loss to tamp down inflation.
BM&FBovespa makes modifications to the index every four months. A new Bovespa index weighting scheme this year takes into account market value as opposed to trading volume, which was used in previous years.
Shares of mining company MMX Mineração e Metálicos SA were added to the benchmark index on Monday while shares of medical diagnostics firm Diagnósticos da América SA, known as Dasa SA, and logistics firm Prumo Logistica SA, formerly known as LLX, were removed.
(Reporting by Asher Levine; Editing by Sofina Mirza-Reid)