NORTH AMERICA: Residents in Toronto were warned to turn off their air conditioners and avoid doing laundry or watching television from 8 a.m. to 8 p.m. today, as the authorities in Canada and the US faced up to the threat of a recurrence of the power breakdown that left 60 million North Americans sweltering in the dark.
In Ontario, Ohio and Michigan, where power was not substantially restored even 24 hours after the lights came back in New York City on Friday, officials urged conservation and patience.
In Toronto - which begins its working week today with a 50 per cent cut in electricity - and other affected areas of Ontario, consumers were warned to avoid excessive use of electricity that could bring the grid down again. "If people don't cooperate, the system will break," said Mr Jim Young, Ontario's commissioner of public safety.
Ontario's premier, Mr Ernie Eves, called on industry and the public to halve electricity use to help a fragile system.
Non-essential workers were told to consider staying at home.
In Ohio, the message was safety, and officials warned Cleveland residents to boil water because of fears that sewage might have contaminated water supply systems.
All of New York City's power was restored on Friday evening. By Saturday, the subway was running on time in all of its boroughs. But the breakdown was estimated to have cost New Yorkers $500m in lost income.
The continued vulnerability of North America's power supply was a constant theme during a flurry of television appearances by the US energy secretary, Mr Spencer Abraham.
He warned that America's ageing power grid had not kept pace with rising demand over the past decade.
"There is peril ahead if we don't modernise this system, invest in energy the way we need to, because there will be other evidences of problems coming up," he said.
Canada and the US have formed a joint task force to investigate the causes of the blackout, and to ensure it does not happen again.
However, Mr Abraham's prescription for a long-term solution appeared controversial. He said America needed a new energy strategy - including a suggestion to drill for oil in Alaskan nature preserves.
The proposal set the stage for a new debate between Democrats and Republicans over the costs of deregulating America's power industry, and the need for investment in the grid.
As the search for the cause of the breakdown continued, consensus was building around the theory that the blackout could be traced to three overloaded transmission lines.
The installation is owned by a small firm based in Akron, Ohio, called FirstEnergy Corp, where a system designed to flash a red warning light on computer monitors was not operational on Thursday afternoon, when the lines began failing.