Large collapse in electric power system on Tuesday left the largest Brazilian city of Rio de Janeiro and Sao Paulo in the dark for two hours. Other parts of Brazil and adjacent Paraguay remained without electricity for 20 minutes after Itaipu power plant ceased to work.

When the giant Itaipu hydropower system discontinued its regular production of 17.000 megawatts, interruption of power affected Rio de Janeiro, Sao Paulo and at least several major Brazilian cities, said Brazilian Minister of Mining and Energy, Edison Lobao.

In his words, the collapse of the electrical energy system affected nine out of the 27 states of Brazil, a country with 190 million people.

Entire Paraguay remained without electricity for 20 minutes

The cause of the collapse is still unknown, but the minister Lobao said that it was likely to blamed on the strong river torrents that tore down the trees near the Itaipu Dam just before it malfunctioned.

Electricity in Rio de Janeiro returned on Wednesday, about half an hour after midnight.

Paraguay's national power company blamed the power-outage on a short-circuit current in the sub-station near Sao Paulo, claiming that it caused a breakdown of the system which supplies Itaipa. According to leading national paper, ABC Color, the entire Paraguay was without electricity for 20 minutes.