Millions in Spain, Portugal, and parts of France were hit by a massive power outage on Monday.

The blackout, which hit most of the Iberian Peninsula, began was first reported around lunchtime local time.

In an X post, Spain’s grid operator, Red Eléctrica, said the causes of the blackout were being analyzed, and all resources are being dedicated to solving them.

In a follow-up post, Red Eléctrica said that parts of the south and north of the peninsula are recovering power as of 1 p.m. local time, and that it continues to work on restoring full service.

The operator estimates that it will take between six and 10 hours to restore the entire power, per the Spanish news agency EFE.

Meanwhile, Spain’s National Cybersecurity Institute is investigating whether the blackout could have been caused by a cyberattack, according to local media reports.

The blackout halted operations at train stations, airports, businesses, and major buildings across affected areas.

Customers faced with powerless food stands in Barcelona on Monday. Sandra Montanez/Getty Images

A metro station in Madrid in the dark during a widespread power outage in Spain on Monday. Burak Akbulut/Anadolu via Getty Images

The empty tennis court on day seven of the Mutua Madrid Open tennis tournament on Monday. Julian Finney/Getty Images

Fans walked through the dark gangways during a general power blackout at the Mutua Madrid Open tennis game in Madrid on Monday. Julian Finney/Getty Images

Fans walked through the dark gangways during a general power blackout at the Mutua Madrid Open tennis game in Madrid on Monday. Julian Finney/Getty Images

This is a developing story. Please check back for updates.