A government investigation into the massive blackout that struck the Iberian Peninsula in April has determined that a voltage surge in the power grid triggered a chain reaction that led to widespread disruptions, Spanish media reported, citing an official statement following a cabinet meeting.

Minister for the Ecological Transition, Sara Aagesen, stated that the causes behind the outage on April 28 were “multiple,” but emphasized that the key failure was the grid’s inability to manage voltage fluctuations that day. The system lacked sufficient capacity to stabilize voltage levels, she explained.

A surge occurs when the voltage in an electrical system exceeds safe levels, overwhelming infrastructure and leading to automatic shutdowns of parts of the grid. Such surges can stem from oversupply, lightning, or failure in protective mechanisms. If not managed promptly, the result can be a cascade of disconnections across the system.

The blackout brought major cities across Spain and Portugal to a standstill, temporarily disrupting internet and phone networks, halting train operations, and affecting even parts of southwestern France. In response, Spanish Prime Minister Pedro Sanchez quickly announced the formation of a commission of inquiry under the Ministry for the Ecological Transition, urging the public to wait for official findings rather than speculate.

Minister Aagesen also pointed to actions by the national electricity operator REE and unnamed energy firms, saying that some of these entities shut down power plants inappropriately to safeguard their infrastructure. These decisions, she noted, made the situation worse. “Because of these missteps,” Aagesen warned, “we reached a critical point - an irreversible chain reaction that could have been prevented with earlier intervention to manage the surge.”