The 1999 Southern Brazil blackout was a widespread power outage (the largest ever at the time) that occurred in Brazil on March 11 to June 22, 1999. The blackout involved São Paulo, Rio de Janeiro, Minas Gerais, Goiás, Mato Grosso, Mato Grosso do Sul and Rio Grande do Sul, affecting an estimated 75 to 97 million people and it lasted 103 days. A chain reaction was started when a lightning strike occurred at 22h 16m at an electricity substation in Bauru, São Paulo State causing most of the 440 kV circuits at the substation to trip. Brazil was undergoing a severe investment crisis during 1999, which limited spending on maintenance and expansion of the power grid. With few routes for the power to flow from the generating stations via the 440 kV system (a very important system to São Paulo state, carrying electricity generated by the Paraná river) a lot of generators automatically shut down because they did not have any load. The world's biggest power plant at the time, Itaipu, tried to support the load that was no longer being supplied by the 440 kV power plants, but the 750 kV AC lines and the 600 kV DC lines that connected the plant to the rest of the system could not take the load and tripped too.