Exxon has told Brazilian officials it discovered oil in deep water off Rio de Janeiro, near massive fields that could hold as much as 80 billion barrels of oil.
State media said Wednesday that Exxon Mobil did not estimate the size of the find in a filing with Brazil's National Petroleum Agency.
Agencia Brasil reported that the company said it is drilling one well and plans another. A Brazilian division of Exxon told the news agency other details are confidential.
Exxon has a 40 percent stake in the block under exploration. Agencia Brasil said U.S.-based Hess has a 40 percent stake, and Brazil's Petroleo Brasileiro holds 20 percent.