A massive blackout hit Spain, Portugal and part of southern France on Monday, grid operators said, leaving millions of people affected.

The cause for the outage was not immediately reported.

Spain’s railway operator Adif said that the power cut halted trains across the entire country, while airports operator Aena said “several incidents” occurred in Spanish airports.

Mobile phone networks went down. AFP reporters in Madrid and Barcelona saw many inhabitants coming out into the streets, holding their smartphones up to try to connect to a network.

Many people had to use the radio instead of the inaccessible internet to get news on the situation.

Many traffic lights had ceased to function, forcing vehicles to slow down to avoid collisions, while metros and trains were halted. Spain’s national road authority DGT urged motorists to stop using the roads.

Spanish Prime Minister Pedro Sanchez was on his way to the headquarters of the state electricity network operator Red Electrica to be briefed on the emergency, his office said.

Portugal’s REN operator said in a statement to AFP that the entire Iberian Peninsula was affected by the blackout, as well as part of France, adding that the outage occurred at 11:33am.

Spain’s Red Electrica said it had managed to start restoring power in the north and south of the country but the problem was not yet resolved. “We are continuing to work to bring back power,” it said.

Spain’s El Pais newspaper posted photos on its website of stopped metro trains in Madrid, police directing traffic, and its own reporters working in a darkened office by the torchlight.

Power cut interrupts play at Madrid Open

Play was interrupted at the Madrid Open on Monday when the city lost power, after world number four Coco Gauff and rising Russian star Mirra Andreeva booked their quarter-final spots.

On Centre Court, the match between Bulgaria’s Grigor Dimitrov and British qualifier Jacob Fearnley was suspended when the Bulgarian was leading 6-4, 5-4 with his opponent serving to stay in the match.

“The outage is preventing the use of electronic line calling systems and also left a spider cam dangling over the court inside Monolo Santana Stadium,” the ATP said on its website.

Tournament organisers said on social media they were “working to restore” power “as quickly as possible”, without giving a timetable.