Authorities are investigating the cause of a massive power blackout that affected tens of millions of people in Argentina, Uruguay and Paraguay.
As power is restored, experts are still largely in the dark about what caused the collapse of the interconnected grid system.
Argentinian president Mauricio Macri promised a thorough investigation into what he called an “unprecedented” outage.
The blackout raises questions about flaws in South America’s grid, which connects many of the region’s largest countries.
Energy officials said the results of the investigation will be available in 10 to 15 days.
They could not immediately provide details on the economic impact of the blackout, which came on a Sunday, and a day before a national holiday in Argentina.
Argentina’s power grid is generally known for being in a state of disrepair, with substations and cables that were insufficiently upgraded as power rates remained largely frozen for years.
The country’s energy secretary said the blackout occurred about 7am local time when a key Argentine interconnection system collapsed.
The Argentine energy company Edesur said on Twitter that the failure originated at an electricity transmission point between the power stations at the country’s Yacyreta dam and Salto Grande in the country’s north-east.
An Argentine independent energy expert said that systemic operational and design errors played a role in the power grid’s collapse.
“A localised failure like the one that occurred should be isolated by the same system,” said Raul Bertero, president of the Centre for the Study of Energy Regulatory Activity in Argentina.
“The problem is known and technology and studies (exist) to avoid it.”
In Paraguay, power in rural communities in the south, near the border with Argentina and Uruguay, was also cut. The country’s National Energy Administration said service was restored by afternoon by redirecting energy from the Itaipu hydroelectric plant the country shares with neighbouring Brazil.
In Argentina, only the southernmost province of Tierra del Fuego was unaffected by the outage because it is not connected to the main power grid.
Brazilian and Chilean officials said their countries had not been affected.
Many residents of Argentina and Uruguay said the size of the outage was unprecedented.
“I was just on my way to eat with a friend, but we had to cancel everything. There’s no subway, nothing is working,” said Lucas Acosta, a 24-year-old Buenos Aires resident.
This is the biggest blackout in history, I don't remember anything like this in Uruguay
“What’s worse, today is Father’s Day. I’ve just talked to a neighbour and he told me his sons won’t be able to meet him.”
“I’ve never seen something like this,” said Silvio Ubermann, a taxi driver in the Argentine capital. “Never such a large blackout in the whole country.”
Several Argentine provinces had elections for governor on Sunday, which proceeded with voters using their phone screens and built-in flashlights to illuminate their ballots.
“This is the biggest blackout in history, I don’t remember anything like this in Uruguay,” said Valentina Gimenez, a resident of the capital, Montevideo.