`Number of factors' triggered blackout

The findings could come as early as mid November.

Abraham would not give specifics because some report details must be cleared up with Canadian officials.

He made clear, however, that no single smoking gun will be cited as the cause of the Aug. 14 blackout that darkened parts of eight U.S. states and Ontario.

"I think you're going to see there are a number of factors that emerged during this investigation as being ... causes or partial causes," said Abraham.

Abraham said the U.S.-Canadian task force investigating the blackout has been scrupulous in trying to be accurate in its findings, but will open its interim conclusions to a review by other parties, who might want to challenge some of the conclusions.

Those suggestions would be considered before a final report and recommendations were issued, he said.

Investigators have concluded that many of the problems on the day of the blackout began in Ohio, where a number of power lines belonging to First Energy Corp. failed during the hour before the power outage.

Investigators also have been examining what influence a number of independent power producers, who were pumping large amounts of electricity through northern Ohio lines on the day of the blackout, might have had on the system.

One theory has been that the system suffered from a shortage of so-called reactive power, essential to maintain voltage needed to push electrons through the system.

The Canadian Federation of Independent Business estimated the massive blackout cost the Ontario economy $1 billion to $2 billion.