A massive power outage spanning parts of Spain and Portugal on Monday brought chaos to airports, train stations, and car travel, and prompted officials to urge residents to stay at home. Parts of France also briefly lost power.

The cause of the outage was not immediately known but the blackout shut down the subway system in Madrid and caused traffic stop lights to go dark across Spain. Madrid’s Metro reported in an X post that the situation was out of its control. 

Play was suspended at the Madrid Open after the venue lost power in the middle of matches. The outage also caused problems with mobile phone networks in Spain. AFP reported people standing in the streets trying to hold their phones over their heads in search of a network connection.

Madrid’s mayor, José Luis Martínez-Almeida, asked residents to stay home and “keep their movements to an absolute minimum.”

Portugal’s energy grid provider Redes Energéticas Nacionais said that power was down across the Iberian peninsula. Lisbon’s Humberto Delgado airport was also hit by the outage.

Portuguese airlines TAP Air told passengers not to head to airports until further notice. “Due to the power cut in several European countries, the operation of airports is temporarily very limited,” the airline shared in a Facebook post.  

The total number of flights affected was unknown but flight tracking site Flightaware showed that almost a quarter of flights at Lisbon’s main airport were delayed.

Stores across large cities in Spain and Portugal were only accepting cash payments due to the outage affecting credit card machines.

Spanish power distributor Red Eléctrica said it could take up to ten hours to restore electricity to large parts of the country.