Much of Spain and Portugal was hit by a widespread power outage on Monday, that canceled flights, brought trains to a halt, downed phone lines and cellphone networks, and left thousands without access to their bank accounts as card payment machines and ATMs were also down.

Power blackouts that left millions of people across Spain and Portugal without electricity may have been caused by a bizarre atmospheric phenomenon, though the true cause is yet to be determined.

Portuguese power grid supplier Redes Energéticas Nacionais (REN) has claimed faults on the Spanish side of the power grid were responsible for the widespread chaos today