Uruguay power company UTE said on social media that power had returned to parts of Montevideo and the southern coast of Uruguay.
"A massive failure in the electrical interconnection system left all of Argentina and Uruguay without power", electricity supplier company Edesur said in a tweet.
"The energy restoration process has begun from the strongest points of the system, the Yacyreta, Chocon and Salto Grande hydroelectric power plants", Argentina's energy secretary said in a statement.
Voters cast ballots by the light of cell phones in gubernatorial elections in Argentina.
A spokesman for Argentine state oil company YPF told Reuters that its La Plata refinery, a critical link in the country's oil infrastructure, had been shut down following the outage. "There's no subway, nothing is working", said Lucas Acosta, a 24-year-old Buenos Aires resident.
"Never in my life have I seen such a enormous power cut", another user wrote. "Sometimes there is not light in the summertime as a result of high electricity consumption, but never such a large blackout in the whole country".
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Investigators spoke with Féliz Garcia at a local hospital and were then able to locate the other five suspects now in custody. Ortiz "continues to recuperate today", his wife, Tiffany, said in a statement released through the Red Sox on Wednesday.
Macri said the blackout had been prompted by a failure in the country´s coastal grid, but said that officials still did not know what had caused the problem. Only the southernmost province of Tierra del Fuego was unaffected.
Elsewhere in Argentina, several provinces were forced to temporarily delay local elections slated for Sunday.
"The causes are being investigated and have not yet been determined", Argentina's secretariat of energy said on its Twitter account, adding it would take "some hours" to restore power completely. "It's very unusual, it's never been this big,", the woman said.
One of Argentina's biggest water companies, Agua y Saneamientos Argentinos, warned those without power to limit their water use, as the distribution of drinking water had been affected by the power cut.
Since taking office, Argentina's President Mauricio Macri has said that gradual austerity measures were needed to revive the country's struggling economy.
"This is the first time something like this has happened across the entire country", Martinez said, according to BBC.