"A massive failure in the electrical interconnection system left all of Argentina and Uruguay without power", electricity supplier company Edesur said in a tweet, commenting on the problem.
"At this moment, we are working to determine the reason for this failure and be able to restore the supply in the shortest possible time", said the official Twitter account of the Provincial Energy Company of Córdoba.
According to news site Infobae, Edesur has confirmed "the blackout is at a country level and also affects Uruguay" and said that nothing like this had ever happened.
Preliminary reports say that the affected provinces in Argentina were Santa Fe, San Luis, La Rioja, Formosa, Chubut, Cordoba, and Mendoza.
"The system is already being lifted from scratch. There are already cities on the coast with service and work is still being carried out towards the general restoration", UTE, the National Administration of Power Plants and Transmissions, stated.
The combined population of Uruguay and Argentina is about 48 million people, however, it is unclear how many people have been affected by the power failure in the region.
The outage comes amid the Copa América football championship in Brazil, while in some parts of Argentina people were preparing to vote in local elections.