NNA - 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.

In Spain, schools and offices reopened, public transport restarted after long delays, traffic gridlock eased and many hospitals had recovered power while others continued to operate on generators.

Spain's electricity grid operator Red Electrica said it was able to supply virtually all of the country's electricity demand on Tuesday morning, while Portugal's equivalent, REN, said that by late on Monday it had all 89 power substations in the country back up and running.

The authorities are now being pressed for an explanation of what caused one of the biggest power outages ever seen in Europe.

Spanish Prime Minister Pedro Sanchez said on Monday night the country had suffered a precipitous loss of 15GW of electricity generation in five seconds at around midday, equivalent to 60% of national demand.

The grid instability caused the Spanish and French electricity interconnection through the Pyrenees mountains to split, resulting in a general collapse of the Spanish system, Red Electrica's chief of operations Eduardo Prieto told reporters on Monday evening. Some areas in France suffered brief outages on Monday.--agencies 

=======R.H.