SAO PAULO, Brazil – A massive 2007 electrical blackout in Brazil has been newly blamed on computer hackers, but was actually the result of a utility company's negligent maintenance of high voltage insulators on two transmission lines. That's according to reports from government regulators and others who investigated the incident for more than a year.

In a broadcast Sunday night, the CBS newsmagazine 60 Minutes cited unnamed sources in making the extraordinary claim that a two-day outage in the Atlantic state of Espirito Santo was triggered by hackers targeting a utility company's control systems. The blackout affected 3 million people. Hackers also caused another, smaller blackout north of Rio de Janeiro in January 2005, the network claimed.

Brazilian government officials disputed the report over the weekend, and Raphael Mandarino Jr., director of the Homeland Security Information and Communication Directorate, told the newspaper Folha de S. Paulo that he's investigated the claims and found no evidence of hacker attacks, adding that Brazil's electric control systems are not directly connected to the internet.

The utility company involved, Furnas Centrais Elétricas, told Threat Level on Monday, it "has no knowledge of hackers acting in Furnas' power transmission system."

A review of official reports from the utility, the country's independent systems operator group and its energy regulatory agency turns up nothing to support the hacking claim.

The earliest explanation for the blackout came from Furnas two days after the Sept. 26, 2007, incident began. The company announced that the outage was caused by deposits of dust and soot from burning fields in the Campos region of Espirito Santo. "The concentration of these residues would have been exacerbated by the lack of rain in the region for eight months," the company said.

Brazil's independent systems operator group later confirmed that the failure of a 345-kilovolt line "was provoked by pollution in the chain of insulators due to deposits of soot" (.pdf). And the National Agency for Electric Energy, Brazil's energy regulatory agency, concluded its own investigation in January 2009 and fined Furnas $3.27 million (.pdf) for failing to maintain the high-voltage insulators on its transmission towers.

Cascading electrical failures like the one in Espirito Santo often have a number of contributing factors, and it's possible that the poorly maintained insulators were only the most conspicuous element in the 2007 incident.

Reports that hackers triggered at least one blackout outside the United States first got wide attention last year, based on comments made by the CIA’s chief cybersecurity officer, Tom Donahue. He declined, however, to identify any country or the specifics of the alleged attacks. The blackout claim even made it into a speech given by President Obama in May. "In other countries cyberattacks have plunged entire cities into darkness," Obama said, not mentioning the cities. In an interview with Threat Level last month, former cybersecurity czar Richard Clarke named Brazil as a hack-attack blackout victim, but didn't provide verifiable details.

In some versions of the story, the hackers were trying to extort money from the utility. The 60 Minutes broadcast this week – which cited six unnamed sources in the intelligence, military and cybersecurity communities – was the first to peg the story to specific blackouts. CBS did not repeat the extortion claim, reporting instead that the location and motives of the hackers are a mystery.

Fallout from the story kept telephones ringing in Brazil's electricity sector Monday. “Everyone’s been calling us all day about it," said a beleaguered spokesman with the National Operator of the Electric System.

Top image: Sao Paolo endures a power outage in 1999.

Dario Lopez-Mills/AP

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