MADRID (AP) — The cause of Spain and Portugal’s widespread blackouts remained a mystery on Tuesday, with some isolated disruption remaining after power was largely restored. One of Europe’s most severe blackouts grounded flights, paralyzed train systems, disrupted mobile communications and shut down ATMs across the Iberian Peninsula on Monday.

Spain faced a massive power outage affecting major regions, with Red Eléctrica confirming gradual restoration. Prime Minister Pedro Sánchez urged public caution while investigations continue. Portugal’s REN cited rare atmospheric conditions as a possible trigger.