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.


Hong Kong nears end of search and rescue mission as tower fire toll rises to 94
National Guard member dies as ambush in US capital becomes political flashpoint
Construction firm bosses arrested over Hong Kong fire; death toll hits 75
FBI raids homes after two National Guard members shot near White House
Pope Leo arrives in Turkey on closely watched first overseas trip