A breakdown in communication and cooperation among Midwest utilities contributed significantly to the worst power blackout (search) in U.S. history, a utility executive has told congressional investigators.

Government and industry officials, testifying at congressional hearings that begin Wednesday, will say it's too early to pinpoint the cause for the Aug. 14 blackout that cascaded from Ohio through Michigan and into Canada and then engulfed New York state.

But in a letter to House investigators, the chief executive of a major Michigan utility says he is convinced that a power plant shutdown and transmission line failures in Ohio "were the triggering event for the blackout" and that an "apparent failure in communication" was a major reason the problem spread.

"For some reason, the required level of communications and coordination failed on Aug. 14, Anthony Earley Jr., chairman and chief executive officer of DTE Energy (search), wrote the House committee. He said this "apparent breakdown in communications between the Ohio utilities and other utility systems" must be addressed.

Earley, whose Detroit Edison (search) serves 5 million people in southeastern Michigan, complained that "Michigan utilities did not have timely or adequate warnings about deteriorating systems condition in Ohio" during the hour before the blackout.

He said Detroit Edison did not begin to detect anything unusual until 4:06 p.m., five minutes before the blackout hit full force in all or parts of eight states. Investigators said the first of five transmission line failures in Ohio began occurring an hour earlier.

In a separate letter to House investigators, FirstEnergy Corp. (search), the Ohio-based company whose generating plant and transmission line failures have been at the center of the blackout investigation, dismissed the notion that a single event triggered the blackout.

"The events of the day were extremely complex and involved thousands of separate and discrete incidents across a widespread multi-system region," H. Peter Burg, FirstEnergy's chairman and chief executive, wrote the committee. "Trying to pinpoint a single event is the wrong focus."

Separately, executives of the International Transmission Co. (search), which operates transmission lines in Michigan, has complained that he did not receive even "a courtesy call" from Ohio utility officials about line problems in that state prior to the blackout.

The House hearing on Wednesday will be the first congressional inquiry into the blackout, which has caused renewed interest in Congress to take steps to increase the reliability of the country's aging power transmission systems.

Energy Secretary Spencer Abraham (search) is to be the leadoff witness. He is co-chair of a U.S.-Canadian task force investigating the blackout and making recommendations to improve the power grid system.

Rep. Billy Tauzin (search), R-La., the committee's chairman, has said he hopes to have a range of electricity proposals as part of a broader energy bill ready for approval by the end of the month.