'More days' needed to identify Spain's blackout origin: govt

Environment Minister Sara Aagesen told El Pais newspaper that "all hypotheses" were being looked at, including a possible cyberattack.

She said the anomaly might possibly have come from solar panels set up in southeast Spain unbalancing the grid, as the network operator Red Electrica has already suggested.

"We know that those installations stopped working in the system," she said.

But she added: "Talking about solar panels (as the cause) might be hasty" and said pointing the finger at renewable energy sources was "irresponsible and simplistic".

The blackout cut electricity across all of Spain, knocking out mobile phone and internet connections, paralysing the rail network and trapping hundreds of people in lifts.

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Experts have questioned whether the necessary balance between supply and demand in the electricity grid had been disrupted, possibly through a sudden fluctuation from wind or solar sources.

Aagesen said Spain has had renewables in its energy mix for a long time and discounted the theory that "a big amount of renewable energy" jolted the grid.

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She pointed out that there had been earlier days with higher solar power generation and lower demand, and the system "had functioned very well".

"Renewable energy allows Spain to achieve a great deal of energy independence in a geopolitically vulnerable world," she said.