Washington ? Hours after the blackout hit, officials were still puzzled Thursday about what caused the power system to fail, and more importantly, why the disruption spread so rapidly and across such a wide region.

Investigators concentrated on transmission lines and transformers in upstate New York and neighboring Canada in search of what might have caused the surge in power that triggered safety mechanisms and shut off the flow of power from New England to Michigan.

American officials were skeptical about a Canadian claim that lightning may have been the cause.

“Such speculation is uninformed and premature,” said William Edwards, president of Niagara Mohawk. He said his utility reported no equipment damage and that power losses in the Niagara system were mostly from “safety mechanisms built into our system” to prevent damage. “It’s going to take time for experts to analyze the data and determine the cause.”

Both federal and state agencies, as well as congressional committees, are expected to investigate the blackout and try to determine why measures put in place to isolate grids and keep power disruptions from spreading failed to do so.

The White House said there was no indication that terrorism was involved. President Bush said Thursday night, “We’ll find out why (it happened) and we’ll deal with the problem.”

Whatever happened, the power disruption, which caused havoc from New England to Michigan, is certain to revive the debate over the reliability of an aging electricity transmission system.

Former Energy Secretary Bill Richardson said the nation’s power grid was antiquated.

“We’re the world’s greatest superpower, but we have a Third World electricity grid,” said Richardson, governor of New Mexico.

An energy bill before Congress would allow federal regulators to step in and direct transmission siting if states or regions were unable to do so. But that provision has been opposed by many lawmakers.

A crowd of thousands waits for the chance to board a ferry from Manhattan to the New Jersey side of the Hudson River in New York. Rides on the ferry were being offered for free Thursday.