Poisonings from generators add to storm's death toll.

About 1.5 million homes and businesses in Florida and Georgia remain without power after they were caught in Hurricane Irma's deadly path.

Irma, which ranked as one of the most powerful Atlantic storms on record before striking the US mainland as a Category 4 hurricane on September 10, killed at least 84 people. Several hard-hit Caribbean islands, including Puerto Rico and the US Virgin Islands, suffered more than half the fatalities.

Florida Power & Light, the state's biggest electric company, said it was working aggressively to restore power to the 23 per cent of its customers still in the dark.

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The utility has never before had to deal with a storm affecting its entire service territory, company spokesman Rob Gould said.

"It will go down as one of the largest and most complex restoration efforts in history," he said. "Now we are literally into the house-to-house combat mode."

The storm's death toll grew to at least 33 people in Florida after a woman died of suspected carbon monoxide poisoning from a generator in Palm Beach County, the Palm Beach Post reported.

A total of eight others died in Georgia and the Carolinas. North Carolina reported its first Irma death on Friday, saying a man there also had died of carbon monoxide poisoning from a generator.

Eight elderly people died earlier this week after being exposed to the heat inside a nursing home north of Miami that had been left without full air conditioning after the hurricane.

The deaths at the Rehabilitation Centre at Hollywood Hills, now under police and state investigation, stirred outrage over what many saw as a preventable tragedy and heightened concerns about the vulnerability of the state's large elderly population amid lingering power outages.

"The governor will continue to review all ways to ensure tragedies like this never happen again," Lauren Schenone, a spokeswoman for Governor Rick Scott, said.

Florida's healthcare agency ordered the nursing home on Thursday to be suspended but the centre plans to fight the state's efforts to shut it down.

Nursing home administrators repeatedly called Florida Power & Light and state officials after a transformer powering its air conditioning system went out during the storm on Sunday. It was told service would soon be fixed.

But it was not until multiple patients began experiencing health emergencies, which led to the evacuation of the centre, that the utility company arrived to make the repair, the nursing home said.

However, Florida Department of Health officials said the facility did not indicate the extent of its problems or request assistance in a state monitoring database.

- AAP