Brazil's environmental authorities said they have discovered a 10,000 liter leak at an oil platform in the pristine Bay of Ilha Grande, the second such mishap to threaten this country's shorelines in recent weeks.
Carlos Minc, Environment Secretary in Rio de Janeiro state, said the accident threatens an area considered an ecological treasure with a rich biodiversity.
It occurred at an oil rig run by Modec, a company active in the offshore oil and gas industry around the globe.
The company was levied a fine of 10 million reais (4.1 million euros, $5.4 million USD), Minc said.
A local Modec official, Andre Cordeiro, told the O Globo newspaper that the company was trying to determine the cause of the spill.
Prosecutors in Brazil last week called for a shutdown of Chevron's activities nationwide and said the US oil giant should be fined $11 billion for damage caused by an oil spill last month.
Prosecutors took legal action against Chevron, its Brazilian unit and the contractor Transocean, seeking $11 billion over the spill at a production well at the Frade field, 370 kilometers (230 miles) off Rio de Janeiro state.
In a statement, they pressed for urgent action by federal judges to "suspend all the activities of Chevron," which would have to pay $277 million daily if it failed to comply.