Other reports suggest the spill in the South Atlantic could be as much as 160 barrels. What caused the leak from the production column, essentially a pipeline that connects an underwater wellhead to a drilling platform, is still being investigated.
The platform is operating as part of a well test that is under way in the Carioca Nordeste area, in the Santos Basin, off the coast of Brazil, according to Petrobras.
IBAMA officials announced on their Web site the oil company has five days to report the total extent of the spill.
IBAMA, the Brazilian National Agency of Petroleum, Natural Gas and Biofuels, said it has opened administrative proceedings on the incident, and that aerial surveys of the spill indicated patches of crude oil stretch for 43 square miles and are unlikely to reach the coast.
The well that was connected to the vertical column was producing with a continuous monitoring and logging system. After the rupture, the well was automatically shutdown by the safety system, and it remains closed and in safe condition, said Petrobras.
The Santos Basin, roughly 190 miles offshore from Rio de Janiero, is home to a presalt layer where industry analysis suspects more than 2.1 billion barrels of oil are recoverable. Petrobras is investing heavily in the region and aims to be one of the largest oil companies in the world.
Pumping the oil provides a particular challenge to oil companies because is in ultra deep water regions of the ocean.
It is unclear if Petrobras will be faced with fines from local authorities as was Chevron, which faces several fines since November for a spill in the same offshore region.
Chevron spilled 2,400 barrels of oil back in November.
The Brazilian oil company does not have the cleanest record. According finding by Brazil's domestic news agencies, Petrobras spilled 4,200 barrels of oil in all of 2010, more than the amount allowed by company officials.
Petrobras said Wednesday it has adopted all contingency procedures in response to the rupture.