SAO PAULO - Officials and local news reports said a widespread blackout has hit at least seven Brazilian states in the nation's northeast.

Power was gradually returning to the massive area. It wasn't clear how many people were affected.

One power company official said the cause is not yet known.

Some of the blackouts early Friday lasted only a few minutes, others a few hours and in some areas the power has not yet returned.

The power failure raised questions again about the energy infrastructure in Brazil - a nation that will host the 2014 World Cup and the 2016 Olympics.

In 2009, a massive power failure left more than 60 million people in the dark in 18 states. That failure was ultimately blamed storm damage to transmission lines.