Power was fully restored to New York City after almost 30 hours but northeastern United States was still making efforts to recover from the fallout of the worst ever power failure, even as a joint task force was set up by US and Canada to probe into the cause of the crisis.

Major cities and towns from Midwest to New York were slowly brought back online but aftereffects of the outage would be felt for quite some time. There are still areas without electricity and some of them might remain dark for another day or two, officials said.

In New York, local trains were still not functioning while in Cleveland, water supply was yet to be restored and in several areas, gas supply was yet to stabilise.

Officials said the effects of the power failure would leave a permanent mark on their budgets though it would take a few days to calculate the cost.

In almost nine seconds Thursday afternoon, power supply failed in parts of eight states in the United States and of southern Canada.

President George W Bush, who is monitoring the situation from California, blamed the outage on an 'antiquated' distribution system and called for modernisation of the delivery system.

The joint task force that will seek solutions to help prevent such failures in future will be jointly chaired by US Secretary of Energy Spencer Abraham and Canadian Minister of Natural Resources Herb Dhaliwal, the White House said.