Spanish grid operator Red Eléctrica has dismissed cyber attacks as the cause of Monday’s widespread blackout that left millions without power across Spain, Portugal, and parts of France. Eduardo Prieto, the operator’s director of operations, stated initial findings show no signs of system interference, backing Portuguese Prime Minister Luís Montenegro’s earlier assessment.

The exact trigger remains unknown, with authorities awaiting concrete data before drawing conclusions. Spanish Prime Minister Pedro Sánchez confirmed investigators are working to identify the root cause to prevent future incidents. The outage occurred when 15GW—60% of the grid’s demand—vanished within five seconds, linked to two rapid disconnections in southwestern Spain’s solar-rich regions.

While some speculated renewable energy fluctuations played a role, Sánchez clarified the issue wasn’t “excessive renewables” or supply shortages, noting demand was normal pre-outage. Experts suggest the grid’s frequency—critical to stability—may have deviated from the standard 50Hz, triggering protective shutdowns that cascaded into a blackout.

Questions also arose about Spain’s interconnection with France, including a high-voltage line inaugurated seven years ago. Though the Iberian Peninsula’s limited grid links make it vulnerable, Sánchez credited cross-border connections with France and Morocco, plus gas and hydropower, for restoring electricity.

Portugal’s grid operator REN retracted an earlier claim attributing the outage to atmospheric anomalies caused by temperature swings, denying it issued the statement. As probes continue, the incident underscores the complexities of modern power grids and the challenges of integrating diverse energy sources.