The regulatory body opened probes into grid operator Red Eléctrica - a subsidiary of Redeia - as well as Iberdrola, Naturgy, Endesa, and Repsol. It also indicated that specific power plants are under investigation.
Iberdrola and Endesa declined to comment. The other companies mentioned did not immediately respond to requests for comment.
Several inquiries have analyzed the causes of the massive blackout, which plunged much of Spain and Portugal into darkness for up to 16 hours on April 28, 2025. Most focused on identifying the causes without assigning blame.
The National Commission on Markets and Competition (CNMC) stated that while the infractions did not cause the blackout, they could have affected the functioning of the electrical system and may constitute administrative offenses, necessitating a formal investigation.
The names of the companies under investigation were disclosed on the regulator's website after the market close.
In a report last month, the CNMC recommended measures to mitigate voltage fluctuations in the power grid following the blackout, as well as to strengthen electrical interconnections with France. It did not assign blame, stating that it was examining potential violations separately.
On Friday, the CNMC said it had detected a chain of events that progressively destabilized the electrical system, culminating in the blackout, the immediate cause of which was a voltage surge. It added that some alleged infractions had persisted for long periods, but noted that this did not equate to assigning responsibility to the companies involved.
(Edited by Carlos Serrano)
