Electrical power has been restored to millions of people in eight U.S. states and parts of Canada following a massive blackout last week. But questions remain about the cause of the outage, which highlighted the need to modernize and upgrade the U.S. electric supply system.

The United States and Canada have formed a joint task force to find out why power failed across much of the northeastern United States and Canada's Ontario province.

Investigators suspect the largest power outage in North American history was triggered by malfunctioning transmission lines in Ohio and a broken alarm system that failed to signal trouble.

U.S. Energy Secretary Spencer Abraham said on the television program Fox News Sunday that it is premature to place blame. "I am not going to speculate whether it was a human error, [or] a mechanical error. But what I will commit to is this: Our task force will be very, very robust in its efforts," he said.

Both the Bush administration and members of Congress agree that legislation is needed to ensure the transmission system is upgraded.

But first, said Representative John Dingell, an energy bill must address the immediate problems that plunged his state of Michigan and others into darkness. "My old daddy used to say, 'kill the closest snake first.' And that is what it is, I think we have to do," he said.

Mr. Dingell, who sits on the House Energy Committee, says the price of energy, its availability and the conditions under which it is delivered will be a problem for the United States for a long time.

Among other things, he says, a comprehensive energy bill would address new drilling in the United States to reduce America's dependence on foreign oil.