THE cause of massive power cuts across Spain and Portugal remained a mystery today, after one of Europe’s worst-ever blackouts grounded flights, paralysed Metro systems, disrupted mobile phone networks and shut down cash machines.

Though some isolated disruption remained, more than 99 per cent of Spain’s energy demand was being met by 7am, national power supplier Red Electrica said.

In Portugal, grid operator REN said all 89 power substations were back online and power had been restored to all 6.4 million customers.