It was the second serious European power outage in less than six weeks after a March 20 fire shut down Heathrow Airport in the U.K.

Cyberattack being investigated as possible blackout cause by Madrid court - Spain’s electricity operator had earlier all but ruled out a cyberattack as the cause of the outage

A blackout brought much of Spain and Portugal to a standstill Monday, stopping trains, cutting phone service and shutting down traffic lights and ATMs for millions of people across the Iberian Peninsula.