U.S.-based supermajor Chevron Corp.'s unit in Brazil must pay a fine of 50 million reais (about $28 million) for the oil spill that started earlier this month off the Atlantic coast, the Brazilian Environment Institute, or Ibama, said.

The amount of the fine was revealed during a meeting Monday in Rio de Janeiro between Ibama chairman Curt Trennepohl and Rio de Janeiro state Environment Secretary Carlos Minc, an official spokesman told Efe.

The spill occurred at a Chevron-operated appraisal well in the offshore Frade field, located 370 kilometers (230 miles) off the coast of Rio de Janeiro state in the Campos basin, Brazil's main oil-producing area.

Chevron Brasil Upstream Frade Ltda., San Ramon, California-based Chevron Corp.'s local unit, could be subject to additional fines and penalties from other environmental regulatory agencies, Minc said.

"The fine is the same as 12 years ago and today represents about half the amount it should be. If it were adjusted (for inflation), it would be something along the lines of 116 million reais (some $65 million)," Minc said.

The incident could hurt Chevron's chances of obtaining exploration permits in the future in the pre-salt layer, which is beneath the ocean floor and contains a huge portion of Brazil's oil reserves, National Petroleum Agency, or ANP, director Haroldo Lima said.

Chevron's situation "has become complicated" and it will only be able to gain access to pre-salt reserves in the Frade field for a "specific project" approved by regulators, Lima said.

The spill is an important incident that will be discussed at the next ANP board meeting, Lima said.

The fine imposed by Ibama on Chevron is the maximum allowed by law and existing legislation would have to be changed to increase fines, Environment Minister Izabella Teixeira said.

Chevron, however, may be subject to additional fines, depending on the result of investigations, Teixeira said.

The company's top executive in Brazil, George Buck, estimated on Monday that a total of 2,400 barrels had spilled into the Atlantic.

Chevron said in a statement released on Sunday that it was taking "full responsibility" for the oil spill.

Over the weekend, the head of the Brazilian Federal Police's environmental crimes unit, Fabio Scilar, questioned the legality and methods being used by Chevron to clean up the oil spill along the Atlantic coast.

The San Ramon, California-based company is "pushing" the oil to the bottom of the sea with high-pressure streams of sand, committing an environmental crime by polluting the ocean and endangering coral reefs, Scilar told Brazilian media Saturday.

Chevron, however, denied Scilar's allegations.

"Up to 18 vessels have been in rotating operation to support well plugging operations and sheen cleanup. The vessels are using oil response methods approved by the Brazilian government, such as deployment of containment booms and surface skimming. At no time has sand or chemical dispersants been used in the process," Chevron said.

Chevron Brasil Upstream Frade Ltda., which has a 51.7 percent stake, is the lead operator in the Frade field.

Brazilian state oil giant Petrobras has a 30 percent interest in the project and the Frade Japao Petroleo Ltda. consortium controls the remaining stake.