By Paulo Trevisani

BRASILIA--Brazilian stocks were lower Friday morning following moderate inflation data and after oil producer OGX Petroleo e Gas Participacoes SA (OGXP3.BR) posted a quarterly loss.

As of 9:48 a.m. EDT, the Ibovespa index was 0.9% lower at 54,943 points, according to Tullett Prebon via FactSet.

OGX late Thursday reported a first-quarter net loss of 805 million Brazilian reais ($400 million), compared with a loss of BRL144.8 million a year earlier.

Earlier this week, OGX, which is part of businessman Eike Batista's group, announced the sale of a stake in an offshore oil field to Malaysian state oil-and-gas company Petroliam Nasional Bhd for $850 million.

OGX led decliners in the index, falling 3.75% to BRL0.79 a share. It has fallen 88.7% over the past 12 months.

Mining company MMX Mineracao e Metalicos SA (MMXM3), another of Mr. Batista's companies, was down 3.27% at BRL0.95.

Brazil's largest mining company, Vale SA (VALE5), was down 0.84% at BRL32.87. State-owned oil producer Petroleo Brasileiro SA (PETR4) was 0.49% lower to BRL20.12.

In the banking sector, Brazil's largest private bank, Itau Unibanco Holding SA (ITAUB4), was down 1.11% at BRL34.62.

The biggest winner on the Brazilian stock market was financial-service firm Cetip SA - Mercados Organizados (CTIP3), which was 2.83% higher to BRL25.45. It was followed by retailer Lojas Americanas SA, which was up 0.6% to BRL8.73.

Earlier in the day, private-sector research center Getulio Vargas Foundation said its general price index, or IGP-M, rose 0.03% during the April 21-30 period, less than the rise of 0.42% in the March 21-31 period.

Wholesale prices, which have a 60% weighting in the index, registered a drop of 0.17% in the April 21-30 period, compared with a rise of 0.38% in March 21-31 period. The day before, Brazilian Finance Minister Guido Mantega told reporters that a wholesale prices decline would lower retail prices in one or two months.

Write to Paulo Trevisani at paulo.trevisani@dowjones.com

Subscribe to WSJ: http://online.wsj.com?mod=djnwires