Media playback is unsupported on your device Media caption Businesses in Buenos Aires were affected by the nationwide power cut
Power is being restored to Argentina and Uruguay after a massive electrical failure left large parts of both countries without electricity.
Argentine President Mauricio Macri has promised a full investigation.
Argentine media said the power cut occurred shortly after 07:00 (10:00GMT), causing trains to be halted and failures with traffic signalling.
The blackout was prompted by a failure in an electrical grid that serves both Argentina and Uruguay.
The outage occurred as people in Argentina were preparing to go to the polls for local elections, delaying voting in several regional provinces.
Parts of Paraguay were also affected, a state energy company said.
What do we know about the blackout?
"A massive failure in the electrical interconnection system left all of Argentina and Uruguay without power," electricity supply company Edesur said in a tweet.
Alejandra Martinez, a spokeswoman for the company, described the power cut as unprecedented.
"This is the first time something like this has happened across the entire country."
Citing official sources, Argentine media reported that the outage was linked to a failure in the transmission of electricity from the Yacycretá hydroelectric dam.
Argentina's Energy Minister Gustavo Lopetegui insisted that the country's electrical system was "very robust," but added that the exact cause of this failure was unclear.
"At the moment we're not ruling out any possibility. But we don't think it is down to a cyber attack," he told reporters.
Image copyright AFP/Getty Image caption This woman lit candles when the power went off in her home in Uruguay's capital, Montevideo
Argentine President Mauricio Macri said power had been restored to over 50% of clients. Priority has been given to hospitals.
Uruguay's energy company, UTE, said power had been restored to 88% of customers.
The combined population of Argentina and Uruguay is about 48 million people.
Among the affected provinces in Argentina were Santa Fe, San Luis, Formosa, La Rioja, Chubut, Cordoba and Mendoza, reports said. Tierra del Fuego in the far south was the only area that remained unaffected because it is not connected to the power grid.
In neighbouring Paraguay, parts of Ayolas, Pilar, Villalbín and the border areas of Misiones and Ñeembucú were also without power.
Image copyright Getty Images Image caption Constitucion railway station in Buenos Aires remained in the dark
One of Argentina's biggest water companies, Agua y Saneamientos Argentinos, warned those without power to conserve water, as the distribution of drinking water had been affected by the outage.
Social media reports of the power were widespread - from the capital Buenos Aires in the north, to Mendoza in the west and Comodoro Rivadavia in the south, among many other cities. Residents posted pictures of dark towns and cities and long lines of cars queuing at petrol stations.
"Everything came to a halt. Elevators, water pumps, everything. We were left adrift," Juan Borges, who lives in Buenos Aires, told the BBC.
"There are some elderly people on the eighth floor but nothing happened, because the power cut was short. If it had gone on for longer it would have been a whole different story." he said.
Local media have been showing voters casting their local election ballots in the dark, with mobile phones being used as lanterns.
DanFZ on June 16th, 2019 at 12:31 UTC »
Here in Cordoba, power is still out.
EPEC, the local electricity company, reports this was a failure of the interconnection system, so the power plants of differents sorts are fine and in operating capacity.
Tierra del Fuego province is the only one with no issues, because since they are so far to the south, they are not connected to the main grid.
4G and phone lines are still operational. I work in telecom so I know cell sites have backup batteries from 8 to 16 hrs, while central datacenters have also fuel backup generators, so comms should be fine until they fix the issue.
Uruguay is reportedly already powering up some of their network, but havent said to what extent.
Edit: 16:27 hrs local time, power is back in downtown Cordoba city and apparently in the rest of the city as well.
swingadmin on June 16th, 2019 at 11:38 UTC »
Reports said the power cut had also affected parts of Brazil and Paraguay and occurred shortly after 07:00 (12:00 GMT), causing trains to be halted and failures with traffic signalling.
rangatang on June 16th, 2019 at 11:32 UTC »
How can an area that large lose all it's power? What would have to fail for it to be that widespread?