Power returns to Spain and Portugal. The outage's cause remains a mystery

MADRID — The cause of Spain and Portugal's widespread blackouts remained a mystery on Tuesday, with some isolated disruption remaining after power was largely restored.

One of Europe's most severe blackouts grounded flights, paralyzed train systems, disrupted mobile communications and shut down ATMs across the Iberian Peninsula on Monday.

By 11 a.m. on Tuesday, the Spanish electrical system was functioning normally, electricity operator Red Eléctrica said. Portuguese grid operator REN said power had been restored to all 6.4 million customers.

As life began to return to normal, authorities in Spain had yet to provide further explanation for why the nation of 49 million people lost 15 gigawatts — equivalent to 60% of its national demand — in five seconds.

On Tuesday, Prime Minister Pedro Sánchez said the government's priorities were restoring Spain's electrical system and finding the causes of the blackout so that a similar event ''never takes place again.''

Deaths are investigated

Spanish news agency EFE reported that authorities were investigating five deaths – including three members of the same family — that could be related to the blackout.

The three relatives died in Galicia due to possible carbon monoxide inhalation from a generator, a woman died in Valencia from problems with an oxygen supply machine and another died in a fire caused by a candle in Madrid, EFE said.

Sabotage ruled out

Eduardo Prieto, director of services for system operations at Spain's electricity operator, noted two steep, back-to-back ''disconnection events'' before Monday's blackout. He told journalists that more investigation was needed.

Spain's meteorological agency, AEMET, said it hadn't detected any ''unusual meteorological or atmospheric phenomena," and no sudden temperature fluctuations were recorded at its weather stations.

Portugal's National Cybersecurity Center said there was no sign that the outage resulted from a cyberattack. Teresa Ribera, an executive vice president of the European Commission, also ruled out sabotage.

Travel and tennis resume

The Madrid Open tennis tournament resumed after the blackout caused 22 matches to be postponed. A packed schedule Tuesday included second-ranked Iga Swiatek advancing to the quarterfinals.

At Spain's largest train stations, droves of travelers waited Tuesday to board trains, or to rebook journeys. At Madrid's Atocha station, hundreds stood near screens waiting for updates. Many had spent the night at the station, wrapped in blankets provided by the Red Cross.

By 11 a.m. Tuesday, service on Madrid's subway system was fully restored. In Barcelona, the system was operating normally, but some commuter trains remained suspended in the afternoon because of ''electrical instability,'' the company that runs the service, Rodalies Catalunya, said on X.

In some parts of Spain, commuter and mid-distance services were still suspended or running at reduced capacity.

Emergency workers in Spain said they had rescued around 35,000 passengers on Monday stranded along railways and underground. The blackout was especially disruptive for transit systems, turning sports centers, train stations and airports into makeshift refuges.

Rubén Carión was stranded on a commuter train outside Madrid but opened a window and walked to the nearest station. He and a friend later spent the night in Atocha station.

Sleeping on the floor ''hungry, thirsty and tired,'' the 24-year-old described his experience in two words: ''pure chaos.''

___

Associated Press journalists Helena Alves in Lisbon, Portugal, and Teresa Medrano in Madrid contributed to this report.