Government officials were left scratching their heads in Argentina on Sunday evening, after a historic blackout left over 40 million people without electricity across the country and neighbouring Uruguay.
"We know that at 7.07am there was a system failure on the coast. These are failures that happen persistently in Argentina and in other countries. It is, however, abnormal and extraordinary that a subsequent chain of events could lead to total disconnection" of the power grid, Energy Secretary Gustavo Lopetegui said during a press conference.
Earlier on Sunday, President Mauricio Macri said via Twitter that the situation was an "unprecedented case which will be thoroughly investigated".
The outage, which affected up to 40 million people, interrupted public transport and telecommunication services and cut off water supplies.
The blackout began at around seven o'clock in the morning, just as voters began arriving to polling stations for provincial elections in four Argentine provinces. Voting occurred without major incidents or disruptions, provincial electoral authorities reported.
"It's a matter of milliseconds from the time the system is destabilized to when it cuts out. These are systems of protection which prompt total disconnection. We need to know why it happened", Lopetegui added.
The government has called for the Wholesale Electricity Market Company Administrator (CAMMESA) to report on the incident within the next 15 days.
Lopetegui refused to deny that the attack had been a cyberattack, saying only he would not ignore any hypothesis.