Power was fully back online for residents of Brazil's south, southeast and midwest regions mid-morning on Tuesday, while it continued to return gradually in northern regions, after an "incident" caused outages across the nation.
In Brazil's north and northeast, power was still being restored before 10:30 am local time (1330 GMT), the mines and energy ministry said in a statement.
Some 16,000 megawatts of power was brought down after an "incident," which was still being looked into, it said.
Mines and Energy Minister Alexandre Silveira has "ordered an investigation into the causes of the incident," the ministry added.
Private power firms operating in Brazil were affected by the outages.
Equatorial Energia and Enel Brasil said they were gradually resuming power supply to their clients, while CPFL Energia said supply had already resumed for all customers.
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