It is a "process that will take time", said Pedro Sánchez, in the Spanish parliament, without giving deadlines.

The government leader highlighted that electricity generation and distribution companies in Spain were asked for all the data generated and recorded in 4,200 units of the system between 12:15 pm and 12:35 pm local time on April 28.

The blackout, which left the entire territory of mainland Portugal and Spain without electricity, occurred at 11:33 am in Lisbon (12:33 pm in Madrid) and originated in Spanish territory, according to authorities in both countries, although the causes are not yet known.

Sánchez reiterated that three electricity generation failures were identified seconds before the blackout in southern Spain (the first) and then two more in the southwest of the country, with the investigation now trying to determine whether these disturbances are related to each other and why the Iberian electricity system completely shut down at that moment.

In a speech lasting more than an hour in the Spanish plenary, Sánchez promised again, as he has done several times in the last week, that the government will "get to the bottom" of this matter to find out what happened, "assume and demand political responsibility" and adopt measures to ensure that a blackout like the one last week does not happen again.

Insisting that this is a complex matter, he demanded and promised "rigor, caution, prudence and absolute transparency".

"I can assure you that everything that is discovered will be made public," he said, after saying that the Spanish government "is fully aware" that citizens want to know what happened, and the government too."

"We will not close any debate on false grounds, we will not rush to conclusions," he added, before emphasizing that "to do the job well, technicians need time" and that "the government's responsibility is to respect the complexity of the matter" and "not to generate noise and self-interested debates, as some are already doing."

In this regard, he asked Spaniards to be wary of speeches that try to explain the blackout with a debate between renewable and nuclear energy.

"At this moment, there is no empirical evidence that says that the incident was caused by an excess of renewables or a lack of nuclear power plants in Spain," he said, in a speech in which he accused right-wing and far-right political parties of having embarked, without data or evidence, on an "ideological agenda" and the interests of companies that own Spanish nuclear power plants, which are all due to close between 2027 and 2035.

Sánchez defended, during much of today's speech in parliament, the commitment to renewable energy, which he said was not just the responsibility of the left-wing government in Spain, but a vast "global consensus" in Europe and the world.

The leader of the Spanish government highlighted that these energies increase national and European sovereignty, are more competitive and have allowed electricity prices to fall in the Iberian Peninsula in recent years, in addition to responding to climate change.

Spain will therefore not change anything in its strategy of investing in renewable energy and will continue to invest and promote investment in infrastructures that allow and improve the transition to green energy, he assured.