A massive blackout left tens of millions of people without electricity in Argentina, Uruguay and Paraguay on Sunday. The Argentine president called it an "unprecedented" failure in the countries' interconnected power grid.

 

Authorities were working frantically to restore power, and by the evening, electricity had returned to 98 percent of Argentina, according to state news agency Telam. Power also had been restored to most of Uruguay's 3 million people as well as to people in neighboring Paraguay.

Earlier Sunday, Argentine voters were forced to cast ballots by the light of cellphones in gubernatorial elections. Public transportation was halted, shops closed and patients dependent on home medical equipment were urged to go to hospitals with generators.

"This is an unprecedented case that will be investigated thoroughly," Argentine President Mauricio Macri said on Twitter. 

"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. "What's worse, today is Father's Day. I've just talked to a neighbor and he told me his sons won't be able to meet him."

"This is an extraordinary event that should have never happened," Energy Secretary Gustavo Lopetegui told a news conference. "It's very serious."

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. Lopetegui said the blackout occurred around 7 a.m. local time when a key Argentine interconnection system collapsed. By mid-afternoon nearly half of Argentina's 44 million people were still in the dark.

An Argentine independent energy expert said that systemic operational and design errors played a role in the power grid's collapse.

"A localized failure like the one that occurred should be isolated by the same system," said Raúl Bertero, president of the Center for the Study of Energy Regulatory Activity in Argentina. "The problem is known and technology and studies (exist) to avoid it."

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 Yacyretá dam and Salto Grande in the country's northeast.