Spain and Portugal restored power after suffering the worst blackout in their history. Traffic lights began functioning, and subways resumed service in Madrid and Lisbon. Train and metro operations restarted, and schools reopened. Commuters faced delays returning to work following an outage that brought Spain, Portugal, and parts of France to a standstill. While electricity had returned to most areas by Tuesday, relief was tempered by growing criticism over the lack of clarity on what triggered the massive power failure.

The Madrid Open tennis tournament also resumed on Tuesday after the blackout caused 22 matches to be postponed on Monday. A busy Tuesday saw world No. 2 Iga Swiatek advance to the quarterfinals.

The sudden outage caused a sharp drop in electricity demand, with 60% of Spain’s power load disappearing within just five seconds around midday on Monday.

Spanish grid operator REE on Tuesday ruled out a cyberattack as the cause of the outage. Spain's High Court announced an investigation into the possibility of a terrorist strike. Prime Minister Pedro Sánchez stated that no potential cause had been ruled out.

"We must not rush to conclusions and commit) errors through haste," Sanchez said on Tuesday. "We will find out what happened in those five seconds," he said as quoted by Reuters.

REE reported it had identified two incidents of power generation loss, likely from solar plants in southwestern Spain, which triggered instability in the electrical grid and led to the breakdown of its interconnection with France.

One of Europe’s most severe blackouts on Monday grounded flights, halted metro services, disrupted mobile networks, and shut down ATMS across the Iberian Peninsula.

Over 99% of Spain’s energy demand had been restored by Tuesday, according to electricity operator Red Eléctrica. In Portugal, grid operator REN confirmed all 89 power substations were back online, restoring power to all 6.4 million customers.

Prime Minister Pedro Sánchez on Tuesday said that the government’s priorities were twofold: restoring Spain’s electrical system and finding the causes of the blackout so that a similar event "never takes place again."

In certain areas, commuter and mid-distance train services remained suspended or were operating at reduced capacity.