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. Read the full story

Brazilian officials are disputing the claim by “60 Minutes” and others that a blackout in 2007 was caused by computer hackers. Wired magazine’s blog Threat Level, citing government and investigative sources, reports that the outage “was actually the result of a utility company’s negligent maintenance of high voltage insulators on two transmission lines.” Insulators hang from power lines and are prone to collect debris, which can cause power surges. In this case, officials say soot from nearby fires collected on the insulators.

Threat Level, which has long been skeptical of some of the more extraordinary claims by U.S. officials about cyber threats to critical infrastructure, spoke to the utility company involved in the blackout and got a denial of any hacker involvement. The company “has no knowledge of hackers acting in [the] power transmission system,” TL reported.

News of the “60 Minutes” piece hit the wires on Saturday, and over the weekend, Brazilian government officials started batting down the story. A senior homeland security official in Brazil told newspaper Folha de S. Paulo that he had investigated the allegations of a hacker causing the blackout and found no traces. Read the full story