Prosecutors have focused on $500,000 believed to have gone to an individual hired to secure government permits to construct two stores in Brazil's capital, Brasilia, between 2009 and 2012, according to the report. Investigators are assessing whether Wal-Mart employees knew about or approved of the suspected payments.
It is not yet clear if anyone will be charged, the report said.
"As we've said from the beginning, we are cooperating fully with the government in this matter and can't comment further on that process," a Wal-Mart spokesman told the Journal.
The retail giant did not immediately respond to CNBC's request to comment.
The investigation initially looked into Wal-Mart's practices in Mexico and found little evidence of major offenses.