Spanish authorities say the massive power outage in April across Spain and Portugal was due to technical and planning errors that led to a cascade of failures in the grid.

Spanish grid operator Redeia blamed power plants for the massive blackout that affected the Iberian peninsula in April, as it disputed a government report that said its failure to calculate the correct energy mix was a key factor.

In April, a massive blackout paralyzed Spain and Portugal for hours. A new government report has revealed the cause.