BUENOS AIRES -- Large parts of South America were hit by a massive power outage early on Sunday, leaving millions without electricity and bringing public transport in Argentina's capital to a halt.
Argentinian energy company Edesur said that the blackout started at 7:07 a.m. local time (1007 GMT), some 50 minutes before sunrise. Neighboring Uruguayan energy company UTE, which said the outage started a minute earlier, said it had left the entire country without service.
Edesur confirmed all of Argentina, with 44 million inhabitants, and Uruguay, with 3.3 million, had been hit by the outage.
The system was shut down automatically because a voltage destabilization was detected, Argentina's Energy Secretary Gustavo Lopetegui said at a press conference.
On a Sunday without extreme temperatures, the grid has a power reserve of 20%, so the complete shutdown was not normal, he said.
Lopetegui did not rule out a cyberattack, but did not consider it to be the leading hypothesis. A result of the ongoing investigations will be known only in seven to 10 days, he said.
In the Greater Buenos Aires area electricity was restored after a few hours, and eight hours after the blackout started, 56% of customers in Argentina were reconnected to the grid, Lopetegui said. Normalization should take several hours.
The blackout hit during Argentina's winter, when the country relies on heating, and one witness named Sara told dpa it was cold on the Argentinian coast south of Buenos Aires at the time of the outage.
Traffic lights were not working, and it was also not possible to refuel cars. "It's very strange, it's never been this big," the woman said.
The outage comes as Argentina is suffering from a severe economic crisis, and also as four provinces were staging local elections.