Energy Secretary Spencer Abraham (search) on Wednesday promised a thorough investigation of last week's blackout as he headed to the first full meeting with his Canadian counterpart on an international task force.

Abraham said the U.S.-Canadian panel would turn to top researchers and industry analysts to determine what led to the blackout and identify ways to prevent a recurrence.

"Like me, President Bush recognizes that we owe the nation a full investigation and determination of what happened," Abraham said at a news conference.

He promised to "investigate why the blackout occurred, how it spread to such a large area and to identify action that needs to be taken to make sure such an event never happens again."

Abraham planned to hold the first meeting of the task force later Wednesday in Detroit. He appeared in Ohio with Gov. Bob Taft and Cleveland Mayor Jane Campbell, whose city lost both power and water service during the blackout.

Abraham and Canada's Minister of Natural Resources Herb Dhaliwal (search) will co-chair the task force.

Grid operators in New York, Michigan, Ohio and New Jersey — which lost power — and New England, which mostly did not, have gathered data for the investigation. Utility regulators in New York also announced Wednesday they would start their own inquiry into the outage. According to the state Public Service Commission, 89 percent of New York customers lost power.

Experts studying the outage have pointed to a series of small failures that may have combined to unleash a huge wave of destructive electricity.

Four otherwise innocuous events occurred Thursday afternoon on the northeast Ohio power grid owned by FirstEnergy Corp. (FE) They include unexplained voltage swings that the company said brought down a coal-fired generator, a pair of power line outages — one caused by a tree — and the failure of an automated warning system.

"In order to have a big problem, you have to have three or four bad things happen all at the same time," said Hoff Stauffer, a power transmission consultant with Cambridge Energy Research Associates (search).

The U.S.-Canadian team will examine the computer logs detailing these failures when they take over several separate investigations already under way. Officials close to the investigation have said an interim report could be released by mid-September, although a final report may be months away.

Technicians from the Federal Energy Regulatory Commission (search) will be joining the U.S.-Canadian task force, FERC commissioner William Massey said Tuesday.

"This blackout should not have occurred. We need mandatory rules for the grid and we need tough penalties for violators," Massey said, echoing statements made by Bush and members of Congress since the blackout.

Abraham said Wednesday the responsibility for paying for improvements would fall on the energy companies. "At the end of the day, the companies and the users are going to have to obviously pay," he said in a televised interview.

Experts say investigators may not find a single event that triggered the cascade of shutdowns. Akron-based FirstEnergy (search) was beset by at least three collapses Thursday.

FirstEnergy has been criticized for other power outages. Earlier this year, the Cleveland suburb of Solon lodged a complaint with the Ohio Public Utilities Commission (search) over outages in May and June that were blamed on outdated equipment and inefficient tree-trimming.

City officials filed the complaint after three meetings between the utility and city council failed to end the outages, said David Kovass, an attorney representing Solon.

"We heard reports of tree branches falling on the lines," Kovass said. "They had surges and dimming. On Memorial Day weekend, they had power outages that would last four to five hours at a time."

None of Thursday's individual glitches would be enough to kill a city's lights on a normal day, and the grid is designed to work around one or two failures, but not more, Stauffer said.

The big questions that need answering, Stauffer said, are the reasons behind intra-grid failures that allowed the blackout to spread like a computer virus from FirstEnergy's lines around Cleveland into the neighboring utility network in Michigan.

After darkening Detroit, the plague spread into Ontario, darkening Toronto, and then south into New York state, where it finally toppled the grid that feeds New York City.

Amid such debacles, many things worked as they should have, Stauffer said. Power networks that lock into FirstEnergy — including those operated by PJM Interconnection (search) and American Electric Power (search) — did seal themselves off, saving Boston, Philadelphia, Pittsburgh, Columbus, Ohio, and other cities from the same fate.

"Why didn't Michigan separate itself from FirstEnergy, like PJM and AEP?" Stauffer asked. "If they'd have done that Detroit would have been all right. Ontario would've been all right. And New York would've been all right."