The CEO of Brazilian state-controlled oil company Petrobras, Maria das Graças Silva Foster, termed as "exceptional" a new crude discovery off the coast of the northeastern state of Sergipe, although she did not provide further details.

"What we're not doing is revealing numbers because we can't. We're conducting tests, and this is in fact a big discovery, an exceptional discovery. And Petrobras needs big discoveries," Foster said Tuesday during the World Steel Association's annual conference.

The Sergipe state government, meanwhile, called the find the "largest discovery in the world" in 2013, and Gov. Jackson Barreto told reporters in Aracaju, the state capital, that Mines and Energy Minister Edison Lobao would make an official announcement on Oct. 23.

Rumors about the discovery sent Petrobras' share price on the Sao Paulo Stock Exchange soaring last week, even though Moody's on Oct. 3 cut the company's long-term credit rating over cash-flow concerns.

The new crude find is located closer to shore and could be cheaper to develop than other offshore, "pre-salt" reserves located further south.

The pre-salt frontier, a series of ultra-deep oil fields that were discovered in recent years and stretch for some 800 kilometers (500 miles) off the coasts of the southeastern states of Espirito Santo, Rio de Janeiro, Sao Paulo and Santa Catarina, could dramatically increase Brazil's proven-reserve tally and transform the country into a major crude exporter.

But accessing those fields, so-named because they are located under water, rocks and a shifting layer of salt at depths of up to 7,000 meters (22,950 feet) below the surface of the Atlantic, will be very costly and pose an enormous technical challenge.

Separately, nine oil companies met a Monday deadline to deposit financial guarantees ahead of a scheduled Oct. 21 auction of the country's largest pre-salt field, Libra, which authorities say could eventually produce up to 1 million barrels per day.

Libra will be the first pre-salt field put up for auction under a new production-sharing regime in which the government is the owner of the reserves.

The head of Brazil's ANP oil regulator, Helder Quieroz, did not indicate which companies deposited guarantees and if any consortiums had been formed, although the depositors were among a group of 11 firms that registered for the auction.

They included the China National Petroleum Corporation, Anglo-Dutch Shell, Colombia's Ecopetrol, Petrobras, France's Total, the China National Offshore Oil Corporation and the Spanish-Chinese consortium Repsol/Sinopec.

U.S. oil supermajors ExxonMobil and Chevron and Britain's BP and BG Group decided not to participate in the auction. EFE