Experts investigating the largest power cut in recent European history, which plunged cities in Spain and Portugal into darkness on Monday and left tens of thousands of people trapped on trains, have ruled out the possibility of a cyber-attack.
According to Spain’s electricity operator, Red Eléctrica, Monday’s blackout was not the result of a targeted attack.
Speaking on Tuesday morning, the operator’s head of services, Eduardo Prieto, said preliminary investigations meant “we can rule out a cybersecurity incident”.
Prieto added that there was nothing to suggest “there was any kind of intrusion into the Red Eléctrica control system”.
He said two consecutive events, which took place at 12.32pm on Monday and then a second and a half later, pointed to a “generation disconnection” that had cut off the supply across the peninsula. While the system weathered the first event, it could not cope with the second. Prieto said the problem had originated in south-west Spain, which is where much of the country’s solar energy is generated.
By Tuesday morning, all of Spain’s electricity substations were up and running, and 99.95% of the country’s power supply had been restored. Across the border in Portugal, the electricity operator REN said all substations were fully operational and the national network had been “perfectly stabilised” by 11.30pm on Monday.
Late on Monday night, after a day of rumour and wild conjecture, Spain’s prime minister, Pedro Sánchez, said experts were working to restore full power and to find out what had caused the blackout.
“That’s something that has never happened before,” he said. “What prompted this sudden disappearance of the supply is something that the experts still haven’t been able to determine. But they will … All potential causes are being analysed and no hypothesis or possibility is being ruled out.”
Sánchez said the power cut originated at 12.33pm on Monday, when, for five seconds, 15 gigawatts of the energy that was being produced – equivalent to 60% of all the energy that was being used – suddenly disappeared.
Related: ‘People were stunned’: how massive blackout unfolded across Spain and Portugal
The prime minister, who chaired another meeting of the national security council on Tuesday morning, thanked people for “once again showing exemplary responsibility and public spirit”.
In a statement early on Tuesday, Spain’s national meteorological office, Aemet, appeared to rule out the weather as a possible culprit.
“During the day of 28 April, no unusual meteorological or atmospheric phenomena were detected, and nor were there sudden variations in the temperature in our network of meteorological stations,” said Aemet.
REN also said it had not sent a message circulating on social media on Monday attributing the blackout to a rare atmospheric event.
The message, in Portuguese, claimed the shutdown was due to “a fault in the Spanish electricity grid linked to a rare atmospheric phenomenon”.
“REN confirms we did not put out this statement,” a spokesperson told Agence France-Presse.
All of Spain’s airports were operating on Tuesday morning, but the transport ministry advised people to check with their airlines for possible changes and to find out whether they would be able to get to the airport on public transport.
The state rail operator, Renfe, said the country’s train network, which was badly hit by the blackout, was gradually returning to normal but that local train services were suspended in regions including Murcia, Extremadura and Andalucía.
About 35,000 people were rescued from more than 100 trains after the cut hit on Monday.
In Madrid, 150,000 people were escorted to safety from the capital’s metro system after trains stopped dead in stations and tunnels. By Tuesday morning, the city’s metro service had been restored on all but one line, and 80% of trains were in operation for rush hour.
At 11am local time (1000 BST), the president of the Madrid region, Isabel Díaz Ayuso, said the metro system was 100% operational, adding: “All schools are open, as are hospitals, health centres, day centres and care centres. Thanks to everyone who’s made this possible.”
The Catalan regional government said local train services were still being affected by the outage but the underground and bus networks were operating normally.
Widespread outages are unusual in Europe. In 2003, a problem with a hydroelectric power line between Italy and Switzerland caused blackouts for about 12 hours, and in 2006 an overloaded power network in Germany caused electricity cuts across parts of the country and in France, Italy, Spain, Austria, Belgium and the Netherlands.
By 10am, shops in Madrid had reopened and many people were heading to ATMs to withdraw the cash they had been unable to access the previous day.
Spain’s busiest railway station, Madrid Atocha, had turned into an impromptu campsite overnight, with frustrated travellers bedding down on cardboard and items of clothing as they waited for news.
Related: ‘Any radios?’ Rush to buy supplies in Madrid as blackout hits
One distraught couple left the station in tears, while others remained glued to their mobiles trying to contact loved ones and find information amid piles of suitcases.
Ruben Coiran, 24, was returning home to Barcelona and had spent 11 hours stuck in Atocha waiting for news.
“It’s tough – putting up with the cold, bearing the hunger, hanging on … We’re having a pretty rough time,” he told Agence France-Presse.
“There were elderly people, children who haven’t been able to eat for six-seven hours. They don’t have toilets,” added Coran, who works in IT.
“It was more difficult for the elderly and for people with babies.”