Work is underway to restore power to millions of people, following a major outage in Argentina and Uruguay.
Edesur, a major provider to the two nations, confirmed the outage in a tweet earlier.
"A massive failure in the electrical interconnecting system has left Argentina and Uruguay without power", it said.
— Edesur Argentina (@OficialEdesur) June 16, 2019
The company has since said it has begun the process of normalisation which "will take several hours".
Around 34,000 customers have since had their power restored, out of millions of people affected.
Uruguay's electricity service body UTE tweeted: "At 7.06 a defect in the Argentine network affected the interconnected system leaving the entire national territory without service, as did several provinces of the neighboring country."
The Provincial Energy Company of Cordoba said: "The Provincial Energy Company of Córdoba reports that, due to a failure outside Epec, in 500 kV of the national interconnected system operated by Transener, there was a zero-voltage restriction that affected much of the country including the Province of Córdoba, as well as the Province of Córdoba, as well as the Province of Córdoba, as well as areas of Santa Fe, Capital Federal and Province of Buenos Aires.
"At this time, work is being made to determine the reason for the failure and to be able to restore the supply in the shortest possible time."
It has also had a knock-on effect to the water supply in Santa Fe and by areas supplied by AySA.
People have reported blackouts in several regions.
The power outage means trains, subways and the metro cannot run.
It could also impact the regional elections taking place in several parts of Argentina.
Images on local media show some people casting their votes while others hold their mobile phones above them to cast light on the ballot paper.
There are reports that some places opened later for voting because of the power outage.
Argentine website Infobae had reported that the website for the National Entity for Energy Regulation (ENRE) was down.
The site should report power outages in real time.