Brazilian Minister of Mines and Energy Edison Lobao said that an important hydroelectric dam shared by Brazil and Paraguay failed Tuesday night, pushing a large swath of central and southern Brazil into darkness.

In a radio interview, Lobao said that at about 10:30 p.m. (local time), the Itaipu dam shut down completely.

However, he added that power began to slowly return Tuesday night, and authorities expected a restoration of electricity overnight.

The incident at Itaipu caused an outage of 18,000 megawatts, an official at Brazil’s National Electric System Operator said. The official declined to be named because he was not authorized to talk to the media.

The official added that the outage was approximately equivalent to the amount of energy needed to power the state of Sao Paulo and its 20 million residents.

“Everything’s fine,” the official said, adding that as Itaipu rebooted, it would repower the affected regions.

(article source: CNN, image source: Strive4impact.com)