Spain and Portugal's power grids are running smoothly following mass power outages on Monday, state operators have said.
Portugal's entire grid was "stabilized" and all power substations were back online before midnight, grid operator REN RENE.LS said early on Tuesday.
Meanwhile, Spain's electricity grid operator, Red Electrica REDE.MC, said it was able to supply virtually all of the country's electricity demand early on Tuesday, although most trains were still not running.
All of Spain's substations were operating on Tuesday morning, Red Electrica said in a post on X social media. "We keep on working from center of electric control to secure total normalization of the system," it added.
The Madrid underground metro network said it had resumed operating at 8 am (0600 GMT) with 80% of trains circulating, but railway infrastructure operator Adif said most trains nationwide were not operating.
Both countries saw power outages for several hours
A huge power outage hit most of the Iberian Peninsula on Monday morning, bringing both Spain and Portugal to a standstill - grounding planes, halting public transport and forcing hospitals to restrict routine proceedings.
Power supply was gradually restored in both countries from late Monday afternoon and early evening, though some operations were still not able to resume on Tuesday morning.
The cause of Monday's power outage was unclear.
Prime Minister Pedro Sanchez said that the country had suffered a loss of 15GW of electricity generation in five seconds, equivalent to 60% of national demand.
The loss triggered a disconnection of the Spanish and French grids, prompting a general collapse of the Spanish system, Red Electrica's chief of operations Eduardo Prieto told reporters on Monday evening. Some areas in France suffered brief outages on Monday.
Portugal's grid officials suggested the issue originated in Spain
Spain is one of Europe's biggest users of renewable energy sources, but Monday's shutdown has already sparked debate about whether the volatility of supply from solar or wind has made its power systems more vulnerable to such an outage.
The reasons for the loss of power are unknown, Sanchez said, adding no hypotheses are ruled out, he added.
Portuguese Prime Minister Luis Montenegro said there was "no indication" a cyberattack was behind the outage.
Spain's Sanchez spoke to NATO Secretary General Mark Rutte on Monday, NATO sources said in Brussels.