MADRID/LISBON (Reuters) – A huge power outage hit large parts of Spain and Portugal on Monday, paralyzing traffic, grounding flights, trapping people in elevators and leaving power operators scrambling to restore power to millions of homes and businesses.

Some hospitals halted routine work and the two countries’ governments convened emergency cabinet meetings, with officials initially saying a possible cyber attack could not be ruled out. Outages on such a scale are extremely rare in Europe, and the cause could not immediately be established.

Reuters witnesses said power had started returning to the Basque country and Barcelona areas of Spain in the early afternoon, a few hours after the outage began. It was not clear when power might be more widely restored.

Hospitals in Madrid and Cataluna in Spain suspended all routine medical work but were still attending to critical patients, using backup generators. Several Spanish oil refineries were shut down and retail businesses shut.

The Bank of Spain said electronic banking was functioning ‘adequately’ on backup systems, though residents also reported ATM screens had gone blank.

“I’m in a data center, and everything has gone off. All the alarms popped up, and now we’re with the groups, waiting to find out what happened,” said Barcelona resident and engineer Jose Maria Espejo, 40.

In a video posted on X, Madrid Mayor Jose Luis Martinez-Almeida urged city residents to minimize their journeys and stay where they were, adding: “It is essential that the emergency services can circulate.”

In Portugal, water supplier EPAL said water supplies could also be disrupted, and queues formed at stores by people rushing to purchase emergency supplies like gaslights, generators and batteries.

The main Portuguese electricity utility, EDP, said it had told customers it had no forecast for when the energy supply would be “normalized”, Publico newspaper said. It warned it could take several hours.

Parts of France also suffered a brief outage. RTE, the French grid operator, said it had moved to supplement power to some parts of northern Spain after the outage hit.

Play at the Madrid Open tennis tournament was suspended, forcing 15th seed Grigor Dimitrov and British opponent Jacob Fearnley off the court as scoreboards went dark and overhead cameras lost power.

Traffic Jams

Spanish radio stations said part of the Madrid underground was being evacuated. There were traffic jams in Madrid city center as traffic lights stopped working, Cader Ser Radio station reported.

Hundreds of people stood outside office buildings on Madrid’s streets and there was a heavy police presence around key buildings, directing traffic as well as driving along central atriums with lights, according to a Reuters witness.

One of four tower buildings in Madrid that houses the British Embassy had been evacuated, the witness added.

Local radio reported people trapped in stalled metro cars and elevators.

Portuguese police said traffic lights were affected across the country, the metro was closed in Lisbon and Porto, and trains were not running.

Lisbon’s subway transport operator Metropolitano de Lisboa said the subway was at a standstill with people still inside the trains, according to Publico newspaper.

A source at Portugal’s TAP Air said Lisbon airport was running on back-up generators, while AENA, which manages 46 airports in Spain, reported flight delays around the country.

Such widespread outages are unusual in Europe. In 2003 a problem with a hydroelectric power line between Italy and Switzerland caused a major outage across the whole Italian peninsula for around 12 hours.

In 2006 an overloaded power network in Germany caused electricity cuts across parts of the country and in France, Italy, Spain, Austria, Belgium, Netherlands and as far as Morocco.

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(Reporting by Emma Pinedo, Jesus Aguado, Andrei Khalip, Catarina Demony, Aislinn Laing, Dominique Patton; Writing by Nina Chestney; Editing by Andrei Khalip, Bernadette Baum, Mark Heinrich and Timothy Heritage)