Spain and Portugal were hit by a widespread power blackout on Monday that paralysed public transport, caused large traffic jams and delayed airline flights, and utility operators were scrambling to restore the grid.
Restoring power could take between six and ten hours, the head of operations at grid operator REE, Eduardo Prieto, told a news conference on Monday.
Authorities were unable to explain the cause of the outage at least an hour after it occurred, though a possible cyber attack had not been ruled out and investigations were ongoing, officials said. A crisis committee was set up in Spain to manage the situation, according to people familiar with the situation.
The Spanish and Portuguese governments convened emergency cabinet meetings after the outage, which also briefly affected a part of France, which borders northeastern Spain.
Portugal's utility REN confirmed a cut in electricity across the Iberian Peninsula that also affected part of France, while Spanish grid operator Red Electrica said it was working with regional energy companies to restore power.
"All plans for the phased restoration of energy supply are being activated, in coordination with European energy producers and operators," a REN spokesperson said.
"REN is in permanent contact with official entities, namely the National Civil Protection Authority. At the same time, the possible causes of this incident are being assessed."
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.
Spanish radio stations said part of the Madrid underground was being evacuated. There were traffic jams at Madrid city centre as traffic lights stopped working, Cader Ser Radio station reported.
Hundreds of people stood outside office buildings on Madrid’s streets and there was a heavy police presence around key buildings, directing traffic as well as driving along central atriums with lights, according to a Reuters witness.
One of four tower buildings in Madrid that houses the British Embassy had been evacuated, the witness added.
Local radio reported people trapped in stalled metro cars and elevators.
Portuguese police said traffic lights were affected across the country, the metro was closed in Lisbon and Porto, and trains were not running.
Lisbon's subway transport operator Metropolitano de Lisboa said the subway was at a standstill with people still inside the trains, according to Publico newspaper.
A source at Portugal's TAP Air said Lisbon airport was running on back-up generators, while AENA, which manages 46 airports in Spain, reported flight delays around the country.
In France, grid operator RTE said there was a brief outage but power had been restored. It was investigating the cause.