The Bush administration on Tuesday moved to consolidate the investigation into the nation's worst power blackout, saying that an industry watchdog group would forgo its independent probe and work with a U.S.-Canadian task force.

Energy Secretary Spencer Abraham (search), a co-chair of the task force, would not speculate on what might have caused the blackout that cascaded across a vast region from Michigan to New York City last Thursday.

"It is way too early to engage in speculation about the role any [incident] might have had in the overall problem," Abraham told reporters at a news conference.

The North American Electric Reliability Council (search), an industry-sponsored group that monitors power grid reliability, so far has been in the forefront of the investigation. The group has pointed to problems in a number of high-voltage transmission lines in Ohio, belonging to FirstEnergy Corp. (search), saying that is where the power cascade that led to the blackout apparently began.

"It's important that we withhold judgment before all the facts are in," said Abraham.

Abraham said it was felt that there needed to be "one ultimate finding" by a single investigation.

He said that the NERC "has agreed to work with the task force and forgo its own investigation of the incident."

Abraham said, "We applaud ... what they have done so far" but it was felt "the public would not want two or three entities producing their versions of what happened."

Abraham said the task force would use "all the resources at our disposal," including the federal research laboratories as well as experts in private industry.

Abraham gave no estimate on when any findings would be made public.

Other government sources said the task force might issue an interim report by mid-September. Abraham said there was no time table, but that the task force would find answers "as quickly as possible and begin implementing solutions."

"We owe our citizens an explanation of this incident and an assurance that steps will be taken to address the cause," he said.