Spain and Portugal to jointly probe Iberian blackout

One of Europe's biggest ever blackouts disrupted millions of lives in Spain and Portugal on Monday, cutting telephone and internet access, halting public transport and plunging cities into darkness.

But no firm cause for the power outage has yet emerged.

"We will collaborate to identify the causes of the incident and implement the necessary measures to ensure this doesn't happen again," said Spain's Minister of Ecological Transition, Sara Aagesen, following a meeting with her Portuguese counterpart, Maria da Graca Carvalho.

The two officials agreed to act in a "coordinated" manner in their exchanges with European authorities on the matter.

Four days after the power outage plunged both countries into chaos for several hours, authorities and experts have yet to provide an official explanation for its causes.

"It is very important to gather all the information to understand what triggered the incident, which, as you know, occurred on the Spanish electricity transmission network," the Portuguese minister said.

"This is something very complex and it will therefore take some time. We need a lot of data to understand exactly what happened," she told Portuguese media outlets.

Madrid has said that the equivalent of 60 percent of Spain's electricity consumption, or 15 gigawatts, disappeared within five seconds during the outage -- a phenomenon the government described as "unprecedented".

Among the several hypotheses that have been put forward, Spanish authorities said they were investigating a potential cyberattack.

However, Spain's electricity grid operator (REE) has deemed this scenario unlikely and said Tuesday it had detected "no intrusion" in its control systems.

In its account of the events, REE said it had identified as a possible origin of the blackout two separate incidents, which occurred one and a half seconds apart.

One of them may have affected a solar power production in Spain's southwest, REE said.