Officials warned on Thursday that some of the more than half a million homes in Canada, Maine and Michigan that lost power in a severe weekend winter storm might not get their power back for at least another day.

Utility crews worked overnight in the hardest hit regions, with assistance from utilities workers from areas unaffected by the storm. On Thursday morning, more than 101,000 homes in Canada were still without power. Officials said on Thursday that in Michigan, 105,000 homes were also without power and in Maine, 36,000 homes.

The storm is linked to at least 27 deaths; 17 in the US and 10 in Canada. At least eight people were killed by the carbon monoxide gas given off from gasoline-powered generators, and more were taken to hospitals with carbon monoxide poisoning. Utilities companies and state officials warned consumers to not use generators indoors and to look out for symptoms of carbon monoxide poisoning.

Three Canadian provinces experienced power outages – Quebec, Ontario and New Brunswick. At the height of the outages, 300,000 customers in Toronto lost power, though that number was down to 54,000 on Thursday morning.

Toronto Hydro said approximately 82% of its customers had power back on Thursday morning, though some customers said they lost power again shortly after getting it back. This could be caused by crews working in the area and falling trees, according to a spokesperson for Toronto Hydro.

About 105,000 homes in Michigan were still without power on Thursday morning, down from the more than 500,000 homes were without power at the storm’s peak. CMS Energy Corp enlisted help from its offices in the eastern US to restore power quickly, but said some customers may have to wait until Saturday to get power back.

DTE Energy in Michigan said it expects most power to be restored to its customers on Thursday. Crews had restored power to 92% of its customers on Thursday morning, but warned that the weather conditions could hinder recovery.

“Frigid temperatures, snow and higher velocity winds today are making restoration work more challenging, and new power outages have occurred as ice continues to put weight on power lines and tree branches,” according to a DTE Energy update.

State authorities in Maine and Vermont said this is the worst storm to hit the region since 1998. More than 100,000 homes in Maine were without power at the storm’s peak.

Maine utilities companies estimated that some customers will not have power back on Friday, though Central Maine Power said that power could be restored by the end of the day for most of its 24,000 customers still without power.

"We've had two beautiful, sunny days in Maine and the ice isn't going anyplace," Lynette Miller, a spokeswoman for the Maine Emergency Management Agency, told the AP. "They're very concerned about more weight coming down on trees that are already compromised by ice."