By H. Josef Hebert
The Associated Press

Click to view map (PDF file) showing a detailed sequence of tripped transmission lines causing the blackout. (AP photo) | ZOOM |

WASHINGTON - The Ohio utility under intense scrutiny in the biggest blackout in the nation's history said Sunday there were problems, including strange voltage fluctuations, in the Midwest power grid hours before its transmission lines failed.

"What happened ... is much more complex than a few tripped power lines in our system," said Todd Schneider, a spokesman for FirstEnergy Corp., which went on the offensive Sunday after being targeted by investigators.

He said that some of the unusual power conditions occurred "as early as noon" - more than three hours before FirstEnergy's high-voltage lines, which have been investigators' focus, failed.

In a statement late Sunday, Michehl Gent, head of an industry group investigating Thursday's massive power outage, acknowledged that "events that occurred on one utility's system may have been affected by events on utility systems elsewhere" in the power grid.

"Although we may have identified the area where the cascading outages began," Gent said, referring to the lines in Ohio that failed, "any attempt on our part to identify the cause of the outages at this point would be speculative and premature."

FirstEnergy Corp., the country's fourth-largest investor-owned utility company with 4.3 million customers in Ohio, Pennsylvania and New Jersey, for three days has been at the center of the blackout investigation.

Meanwhile, Canadian officials complained that they were not notified promptly when problems began to emerge in the eastern grid interconnection ahead of the blackout. Such notification is required under a 1965 agreement and it "did not happen this past Thursday," said Ontario Premier Ernie Eves in Toronto.

Federal investigators joined industry teams Sunday in the search for clues into what triggered the blackout that left all or parts of eight states dark from Michigan to New York City last Thursday.

Energy Secretary Spencer Abraham promised to move as quickly as possible to get answers and address whatever problem is found, but said so far there's no indication who might be responsible.

"We can't allow it to linger long. We need to address it," said Abraham, who made the rounds of the television talk shows Sunday and repeated a theme of confidence that the cause of the power disruption will be uncovered.

Administration officials acknowledge that the mystery surrounding the start of the blackout may not be easily unraveled.

"It's going to take some time," said Abraham on NBC's Meet the Press. He refused repeatedly during the day to speculate on the cause, whether it was human error or a mechanical glitch, or where the problem might have begun.

The investigation by the North American Electric Reliability Council (NERC) has focused on the likelihood of a combination of mechanical glitches and human failures as it tries to piece together second-by-second events during the hours before the blackout, focusing on power lines in northern Ohio.

NERC, which was created after another major blackout in 1965 to monitor the power grid and set voluntary reliability standards, has said the problem appeared to have cascaded after the breakdown in the three high-voltage lines south of Cleveland in the area serviced by utilities owned by FirstEnergy.

FirstEnergy acknowledged that an alarm that should have flashed a red warning on computer monitors when power was being lost, did not sound in its central control room.

That "certainly contributed to it," said Gent, appearing Sunday on ABC's This Week. But he said the alarm did not fail at other locations where technicians were supposed to monitor the lines.

"We have to dig into this to see why the alarm wasn't noticed by somebody else" in addition to why the alarm was not working at the FirstEnergy control center.

Later, appearing on CNN, Gent said when the third line "tripped" - or lost power - "that should have separated the local system ... and the rest of the grid should have remained intact."