Chevron said after the November leak that it had underestimated the pressure in an underwater reservoir, so that crude rushed up a bore hole and eventually escape into the surrounding seabed some 230 miles (370 kilometers) off Rio's coast. The oil escaped through at least seven narrow fissures on the ocean floor, all within 160 feet (50 meters) of the well head.
"Everything indicates that Chevron was imprudent and that area should not have been developed," said Carlos Minc, the environment minister for Rio de Janeiro state. "The porous seabed has dozens of fissures and faults through which oil seeps."
Minc stressed that the geographic studies of the area of the appraisal well required extreme caution and extra safety measures.
Asked if the government was overreacting because Chevron is a foreign company, Minc said: "I don't think it (the reaction) was excessively rigorous."
He said Petrobras has also been fined for leaks.
"I do not see any 'Chavismo' here," he said referring to Venezuelan President Hugo Chavez's contentious relationship with foreign oil companies.
Rousseff said in a Wednesday speech that foreign oil companies operating in Brazil must "abide by the safety regulations and know they must stay within security limits and sometimes below security limits but never go beyond them."
Rousseff spoke at the inauguration of Magda Chambriard as president of Brazil's National Petroleum Agency. She did not mention either Chevron or Transocean.
Oliveira said the two companies failed to adopt procedures to contain the leak. He wrote that those expected to face charges didn't halt drilling operations soon enough and that when questioned they said the risks involved "were acceptable."
Oliveira says Chevron and Transocean "altered the truth" in documents presented to authorities, such as the number of ships deployed to contain the leak.
"The reckless operation that led to the environmental damage was planned or approved by all (the 17)," Oliveira. "They knew they were drilling in a high-pressure area and that the walls of the well could not withstand that pressure."
Transocean owned the Deepwater Horizon rig that oil company BP PLC was leasing at the time of last year's Gulf of Mexico oil spill, the largest in U.S. history and one that dwarfs the Brazilian leak. At its peak, BP's Macondo well was spewing more than 7.5 million liters a day.
Brazil itself has had bigger oil spills than this one.
In 2000, crude spewed from a broken pipeline at the Reduc refinery in Rio de Janeiro's scenic Guanabara Bay, spewing at least 1.3 million liters into the water. Just a few months later, more than 3.8 million liters of crude burst from a pipeline operated by state-controlled oil company Petrobras into a river in southern Brazil.
Brazil's worst oil disaster was in 1975, when an oil tanker from Iraq dumped more than 30 million gallons of crude into the bay and caused Rio's famous beaches to be closed for nearly three weeks.
Associated Press writer Jenny Barchfield in Rio de Janeiro and Bradley Brooks in Sao Paulo contributed to this report.
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