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.

Spain's government said Tuesday that the massive April power blackout across Spain and Portugal that disrupted businesses, internet connectivity, transit systems and other critical infrastructures

A major power outage that paralysed the Iberian Peninsula in April was caused by "overvoltage" on the grid that triggered "a chain reaction", according to a government report released Tuesday.