ARGENTINA, BUENOS AIRES -- A massive blackout left all of mainland Argentina and Uruguay without power on Sunday for more of than 12 hours, affecting tens of millions of people.

The unprecedented blackout which put under criticism even Argentine President Mauricio Macri, may have affected a population greater than California's, across a region four times the size of Texas: Argentina has more than 44 million people, and Uruguay about 3.5 million, reports The New York Times.

Alejandra Martínez, a spokeswoman for Edesur, an electricity company in Argentina that serves parts of Buenos Aires, called the incident "a complete blackout in Argentina."

Although officials said every possible cause would be considered, Argentina's energy secretary said a possibility of a cyberattack is ruled out.

The cause remained under investigation by late Sunday, when power had been largely restored to both countries.

Source: The New York Times