Power returning in Spain and Portugal after large parts hit by blackout - but what caused it?

Power supplies have been returning in Spain and Portugal after large parts, including the capitals Madrid and Lisbon, were hit by a huge outage on Monday.

Millions of people were caught up in the chaos after the mass blackout brought many areas to a standstill, with trains stopping, planes grounded, internet and mobile phone services cut, traffic lights and ATMs down, and some routine hospital operations suspended. Spain's interior ministry declared a national emergency and the two countries' governments convened emergency cabinet meetings as officials tried to find out what caused the outage which started around 12.30pm (11.30am UK time).

Blackouts in Spain and Portugal: Follow latest updates About half the electricity supplies in Spain have now been restored by the grid operator, Prime Minister Pedro Sanchez said on Monday evening, adding the rest should be back by Tuesday. In a televised address, Mr Sanchez said authorities have not yet worked out what had caused the blackout in the Iberian Peninsula and were not ruling anything out.

He asked the public to refrain from speculation, and urged people to call emergency services only if really necessary. Eduardo Prieto, the head of operations at Spanish power grid operator Red Electrica, said the event was unprecedented, calling it "exceptional and extraordinary".

Meanwhile, Portugal's Prime Minister Luis Montenegro said power in his country would be fully restored in the coming hours. He said all the state services remained operating in the country despite all the difficulties.

He also said there was "no indication" a cyberattack was the cause. Read more: Analysis - How electricity grids fail 'Rare atmospheric phenomenon' Portugal's grid operator Ren claimed the outage was caused by a fault in the Spanish electricity grid, related to a "rare atmospheric phenomenon".

Ren says that, due to extreme temperature variations in Spain, there were "anomalous oscillations" in very high-voltage lines. It also says that given the complexity of the issue, it could take up to a week for the network to fully normalise again.

It comes as France briefly lost power following the outages in Spain and Portugal, French grid operator RTE said. Parts of Madrid underground were evacuated and traffic lights in the city were not working, according to local media.

Play was suspended at the Madrid Open tennis tournament due to the outage - with Britain's Jacob Fearnley forced off court in a critical moment during his third-round tie with Grigor Dimitrov. The loss of power affected scoreboards and the camera above the court.

Organisers later announced the tournament would not be able to resume on Monday, with afternoon and evening sessions cancelled. Airports affected Aena, which runs international airports across Spain, said earlier that "some incidents were occurring" at the airports due to the outage.

The company added in a statement: "Contingency generators are active. Please check with your airline, as there may be disruptions to access and ground transportation." People 'had nowhere to go' Maddie Sephton, who is from west London, was on the Madrid Metro when the power outage occurred.

"We got on the train and everything was fine," she told Sky News. "But then everything went dark." She was stuck on the train for 20 minutes until a staff member opened the doors manually.

Mrs Sephton says she was on her way to the airport at the time - and had to exit the station by walking up 15 flights of stairs with her luggage. "No lifts are operating - making it difficult for elderly people with limited mobility," she added.

Above ground, she said that "everyone is just standing around and waiting". Bars were unable to take card payments, cash machines are down, and traffic lights weren't working either.

"I currently don't have any internet service and just €15 in my wallet - I can't withdraw any money from the ATM," she added. "A couple have offered to let us get a ride in their taxi to the airport.

Their flight is at 4.30pm so they're pretty relaxed - but my flight back to London is at 3pm and I'm nervous." Mrs Sephton said: "People are just walking but have nowhere to go, and nothing to do." Meanwhile, thousands of passengers had to be evacuated after the blackout left the metro service in Barcelona without power. The blackout was also reported to have forced the closure of the city's tram system and rendered some traffic lights there inoperable.

It has also impacted medical facilities, with hospitals in Madrid and Catalonia forced to suspend routine medical work. Staff have been able to attend to critical patients using power from backup generators.

It comes as Metrovalencia, the urban rail system, encompassing both metro and tram services in Valencia, said traffic in the city was "disrupted" due to a "general power outage in the city". The outage also hit the Portuguese capital Lisbon and surrounding areas, as well as northern and southern parts of the country.

Portugal's government said the incident appeared to stem from problems outside the country, an official told national news agency Lusa. "It looks like it was a problem with the distribution network, apparently in Spain.

It's still being ascertained," Cabinet Minister Leitão Amaro was quoted as saying..