Spain's grid operator denied on Wednesday dependence on solar power was to blame for the country's worst blackout, while Prime Minister Pedro Sanchez came under increasing pressure to explain what went wrong.

Electricity is pulsing through Spain and Portugal again after a massive outage knocked out power in both countries on Monday. So too are questions.

The countries’ top officials were trying to determine the cause of an outage that left tens of millions of people across the Iberian Peninsula without power.