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.

BUDAPEST, Hungary (AP) — An unprecedented blackout across Spain and Portugal upended the lives of millions across the Iberian Peninsula, a stark reminder of modern society’s reliance on electricity, and how quickly life can descend into chaos when the grid goes down.

Red Electrica de Espana (REE) on Wednesday said the source of the outage had been narrowed down to two separate incidents of loss of generation in substations in southwestern Spain, but stressed that it was too early to draw conclusions, as it had yet to identify their exact location.