Tuesday's power outage has affected 25 out of 26 states except Roraima, the report said.
Brazil's Operator of the National Electricity System and the Ministry of Mines and Energy said that some malfunction occurred at 8:31 a.m. on Tuesday (11:31 GMT) but have not yet determined the cause of the incident.
Electricity supply has already been restored in the south, southeast and west of the country, the ministry said.
The blackout caused chaos in transportation in a number of cities. In Sao Paulo, the power outage affected the work of several subway lines. In the state of Bahia, passengers had to leave train cars and walk along the tracks. Traffic lights in many major cities of Brazil had been cut off.