Electricity is pulsing through Spain and Portugal again after a massive outage knocked out power in both countries on Monday. So too are questions.

MADRID (AP) — The cause of Spain and Portugal’s widespread blackouts remained a mystery on Tuesday, with some isolated disruption remaining after power was largely restored to both countries.

A massive power outage appears to have affected large portions of Spain and Portugal Monday. Red Electrica, the operator of Spain's power grid, said on social media Monday morning that voltage has been recovered in substations in several areas in the north,