Power began returning to households in Spain and neighbouring Portugal, hours after cities across the Iberian Peninsula were plunged into darkness in one of Europe's most severe blackouts.Investigators are still looking into the cause of the blackout which remains unclear,

Electricity had been restored to most of Spain and Portugal early on Tuesday after huge nationwide blackouts, although authorities were still trying to find out what caused the sudden outage.

A massive power cut hit large parts of Spain and Portugal on Monday, causing widespread chaos and disruption. The outage left millions of people without electricity, while internet and phone networks were also down. Trains were cancelled and evacuated in some regions, traffic lights stopped working amid mounting delays at airports.