Power began gradually returning late Monday to parts of Spain and Portugal after an unprecedented blackout crippled the Iberian Peninsula, disrupting air travel, halting public transportation, and suspending routine hospital services across both nations.

Spain’s Interior Ministry declared a national emergency and deployed 30,000 police officers nationwide, while emergency cabinet meetings were held in both Madrid and Lisbon to coordinate the crisis response. Experts say the scale and suddenness of the outage are virtually unprecedented in modern European infrastructure.

The cause of the blackout remains under investigation. Portuguese officials indicated the problem originated in Spain, while Spanish authorities pointed to a sudden disconnection from France’s power grid. Spanish Prime Minister Pedro Sánchez confirmed the nation suffered a catastrophic loss of 15 gigawatts of electricity—approximately 60% of national demand—in just five seconds. “This is something that has never happened before,” Sánchez said, adding that NATO had been alerted as a precautionary measure.

While Portuguese Prime Minister Luís Montenegro stated there was “no indication” of a cyberattack, speculation about sabotage gained traction. Joao Conceição, a senior board member at Portugal’s grid operator REN, said a massive voltage fluctuation within Spain’s network may have triggered a cascading failure that spread rapidly across the border.

Spain’s national grid operator, REE, attributed the outage to an “extreme and unprecedented” failure in the interconnection with France. “The magnitude of the power loss exceeded what European systems are designed to tolerate,” said REE spokesperson Eduardo Prieto. France’s RTE confirmed it had dispatched emergency electricity supplies to support northern Spain.

By Monday night, Spain had restored around 61% of power, with electricity flowing again in parts of the Basque Country, Barcelona, and Madrid. In Portugal, REN reported that 85 of its 89 substations were back online, including those serving Lisbon.

Madrid Mayor José Luis Martínez-Almeida urged residents to remain indoors due to darkened streets and the need to keep emergency routes clear for first responders.