Brazil is fining U.S. oil giant Chevron $28 million in connection with an oil spill off the coast of Rio de Janeiro state, saying the company could face more fines in the coming days.

Brazilian officials also said Monday that the national government will ask the California-based company to pay for damages caused by the spill near the Frade oil field. Chevron was drilling an appraisal well about 370 kilometers off the northeastern coast of Rio when the spill occurred.

A Chevron official says the company underestimated the pressure in the reservoir being targeted. Chevron has taken responsibility for the leak, saying the problem was discovered November 8 and the situation brought under control a few days later. A company statement said Chevron will continue to cooperate fully with authorities. It is estimated that the leak caused 200 to 330 barrels of oil per day to seep into the Atlantic Ocean over a period of about one week.

Brazilian President Dilma Rousseff also called a meeting with her energy and environment ministers to discuss the issue.

News reports say the spill is a test for Brazil, as huge offshore oil fields have been announced, with estimates they could hold at least 50 billion barrels of oil.