ROME (AP) _ Power went out across Italy before dawn Sunday, plunging the nation into darkness, police and news reports said. Authorities did not immediately know the cause.

There was no official tally of customers without power, but early reports indicated most of Italy's 58 million people could be affected. The Aug. 14 blackout in the eastern United States affected 50 million people.

The first Italian power outages were reported around 4 a.m. local time in Rome, where the city was celebrating an all-night festival with museums and restaurants open around the clock.

Later, the national electricity company ACEA said power was out across the nation, the ANSA news agency said.

``As far as we know it's all across Italy,'' police official Franca Sesti Miraglia said in Rome.

``We don't know the cause yet,'' she said.

ANSA said that hundreds of people attending the all-night ``White Night'' festivities in Rome were stuck in subways due to the blackout. Police could not immediately confirm the report.

``We're not aware of anything really serious. There are some problems,'' Sesti Miraglia said, without giving details. ``With the 'White Night,' there were many people out.''

In the northern city of Milan, civil defense official Pasquale Aversa said a little power had returned there by 7 a.m.

``In certain parts of the city, electricity has already returned, and that is true also in some areas around Milan,'' he said. ``Obviously, there are problems with having a city in the dark. But given the situation we're in, it's going well.''

He added that hospitals and other emergency centers were using generators. Top civil defense officials will likely hold a meeting in Rome on the matter soon, Aversa said, but he had no further details.

Information on the outage was hard to come by: The blackout cut access to television and radio, while some government agencies' phone lines were constantly busy or not responding early Sunday morning.

There were no immediate reports of outages in neighboring countries.

Italy was hit with partial power cuts in June, when people _ suffering in the scorching summer _ overloaded the system with air conditioners and other electricity-guzzling appliances. That was the first time in more than 20 years that the national operator of the electrical grid ordered power cuts.

Authorities have repeatedly said that power demand is growing faster than supply and that imported electricity would not make up for insufficient production in the long term.

By 7 a.m. local time (1 a.m. EDT) power was still out in the capital, and authorities had not yet announced an explanation.

A massive blackout hit vast swaths of the northern and eastern United States and parts of Canada on Aug. 14, affecting 50 million people and shutting down more than 100 power plants.

On Aug. 28, power briefly went out in parts of London and southeast England, shutting off traffic lights in the British capital and stranding hundreds of thousands of people on subways and trains.

Authorities are still investigating the U.S. and British outages.