New Yorkers urged to stay away

Mayor Bloomberg urged New Yorkers to take the day off

New York's mayor has urged people to stay away from the city as electric power is gradually restored to the eastern part of North America, after the worst blackout in US history.

Michael Bloomberg said power should be restored to most New Yorkers later on Friday but that the subway would remain closed for the evening rush hour.

The power cut left thousands of people stranded overnight on the streets of New York, and disrupted trains and international flights as well as causing traffic gridlock.

About 50 million people were affected by the outage which crippled cities from New York to Detroit, and Toronto to Ottawa.

Commentary on TV news is very positive... but a lot of angry people will be asking how it could happen Lucy Elbourne NY commuter's story

Mr Bloomberg, speaking at a press conference, said he expected Saturday to be normal and full services to be restored by Monday.

But he asked all non-essential New York City workers not to report back to work on Friday, urging them to take a day off instead.

Mr Bloomberg said one person had died of a heat-related heart attack and one firefighter was injured battling a fire.

Police and firefighters carried out 800 rescues from lifts, and dealt with more than 80,000 emergency calls while medical services dealt with 5,000 calls.

Click here to see a map of the north American electrical grid

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Asking people to stay away, Mr Bloomberg said there would still be traffic delays on Friday as some traffic lights were still not working.

The city's streets were quiet and traffic was light, said the BBC's Emma Simpson in New York.

The city's beaches will also be shut because of sewage contamination.

Mr Bloomberg said the temperatures were expected to be in the 90sF (30C) on Friday.

New Yorkers were also offered the following advice:

• Stay cool by drinking water, wearing light clothing and keeping the windows open

• Check on loved ones and the elderly

• Conserve energy in areas where power has been restored

• Some city swimming pools will be open as will cooling centres in each of New York's boroughs. 600 sprinklers will be on in city's the parks

• Check perishable foods in fridge

• Do not use the emergency number 911 for non-emergency calls, but 311 to get updates on the situation.

No cause

The exact cause of the blackout has not yet been pinpointed.

But Mr Bloomberg said the power cut began in Canada.

The two countries have an agreement to use each other's power networks as a back-up.

RECENT US BLACKOUTS 1996: 4m people hit by electricity outage across nine states 1977: lightning strike leaves New York without power for 25 hours 1965: power loss in north-east US and southern Canada hits 30m people

Mr Bloomberg said an event in Canada had put extreme demand on the New York power grid and the system collapsed.

"It appears an event took place up in Canada, and that the load shedding that perhaps they should have done was not done in a way that prevented the New York power grid from having to try to supply power."

Lightning strikes have been suggested as the initial cause of the problem by some officials but dismissed by others.

The governor of New York State, George Pataki, has called for a full investigation.

Canadian officials earlier said a fire at a power plant near the upstate New York town of Niagara caused the outage, but US officials dispute that theory, although they say terrorism was not to blame.

Back on line

The failure, which affected some 50m people in the US and Canada, was the biggest in US history, and cities from New York to Detroit, and Toronto to Ottawa left crippled.

It's frightening because the news is eerily reminiscent of 9/11 Matt, New York Power cuts: Were you affected?

Some rural areas in Michigan were reconnected, but authorities warned that more populated urban centres would be powerless into the weekend.

In Canada, power was returning slowly to Toronto and the capital, Ottawa.

But Ontario Premier Ernie Eves declared a state of emergency for Canada's most populous province and urged people to remain at home and save energy and asked them not to drive to conserve fuel.

Businesses were also asked not to operate.

Electricity has also been restored to western and central Toronto and about half of Ottawa, although officials there have warned of more blackouts during the day.