The head of an energy reliability group says he is "personally embarrassed" by a massive blackout in the northeastern United States and Canada, and is working to find the cause.

Michehl Gent of the North American Electric Reliability Council made the comment at a press conference, Friday. He said the non-profit trade group is supposed to ensure the security of power grids and make sure failures don't happen.

Mr. Gent said investigators are focusing on a U.S. distribution route in the state of Ohio, but he declined to confirm it was the cause of Thursday's outage.

Mr. Gent also rejected allegations the blackout started at a power facility in New York or in Canada.

On Thursday, the office of Canadian Prime Minister Jean Chretien said a suspected lightning strike hit a power plant in New York state.

Meantime, the mayor of New York city, Michael Bloomberg, Friday, blamed Canada for the trouble.