Spanish Prime Minister Pedro Sanchez warned of a “long night ahead,” as the worst blackout to hit Europe in over a decade approached the 12-hour mark with no cause clearly identified and an uncertain timeline for the full restoration of power.

Befuddled passers-by holding torches and mobile phones squinted through pitch-black streets early on Tuesday and stranded travellers spent the night at train stations after a crippling backout plunged Spain into darkness.

On Monday morning, millions of people across the Iberian Peninsula lost power. The cause of the outage is yet to be determined.