The blackout that paralyzed the Iberian Peninsula had an especially fierce impact on trains that run across Spain.

Red Eléctrica, Spain’s electricity grid operator, ruled out a cyberattack, human error or unusual weather. Experts say it could take weeks to determine the cause.

BARCELONA, Spain (AP) — The blackout that engulfed the Iberian Peninsula on Monday was chaotic and stressful for many. But it had a silver lining: People were forced away from their screens and into the “real” world, connecting with the present and one another. Some Spaniards and Portuguese embraced their day without power.