Spain and Portugal were hit by a widespread power outage on Monday that paralysed public transport, caused large traffic jams, and delayed flights.
Utility operators sought to restore the grid, but Spanish electricity transmission operator Red Eléctrica said the outage, the cause of which was not immediately known, could last from six to 10 hours. Officials said the possibility that it was caused by a cyber attack had not been ruled out.
The outage caused chaos in parts of Portugal and Spain as traffic lights stopped working, causing gridlock.
Transport networks were halted, hospitals were left without power, and people were trapped in the metro and elevators.
In Madrid, hundreds of people stood in the streets outside office buildings, and there was a heavy police presence around some important buildings, with officers directing traffic as well as driving along central atriums with lights.
The Spanish and Portuguese governments met to discuss the outage, which also briefly affected parts of France, and a crisis committee was set up in Spain, sources familiar with the situation said.
“The government is working to determine the origin and impact of this incident and is dedicating all resources to resolve it as soon as possible,” the Spanish government said.
Red Electrica said it was working with regional energy companies to restore power. Portuguese utility REN said it had activated plans for the phased restoration of the electricity supply.
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.
The European Commission said it was in contact with the authorities in Spain and Portugal and the European network of transmission system operators ENTSO-E to try to establish the cause of the outage.
