Manitoba Hydro is urging customers reeling from a snowstorm that's left them without electricity for days to keep fuel-burning equipment like heaters out of their homes after a woman was found unconscious.

Some people in powerless homes have resorted to bringing generators, patio heaters or barbecues inside, but officials are warning against doing that because, Hydro spokesperson Bruce Owen said, the equipment is not properly ventilated.

A woman outside Morden in southern Manitoba is believed to have lost consciousness from carbon monoxide poisoning on Sunday after a propane heater was hauled into her house. She is now recovering in hospital.

A Hydro crew happened across the scene while trying to restore electricity from an unprecedented storm that's knocked down thousands of trees, downed power lines and forced the province, Winnipeg and many municipalities to call a state of emergency. Around 5,700 people have been relocated.

"A gentleman came out of the house distraught and was saying his wife was unconscious," Owen said.

"We got into the house right away and got her out, where she was able to at least get some fresh air."

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Hydro is asking customers to keep their propane equipment outside.

"Carbon monoxide is an insidious gas. You can't smell it and it just creeps in, and you get tired, you feel ill. You shake it off, thinking there's nothing wrong," Owen said. "The next thing you know, you're unconscious."

Five days after the storm first rolled through, pummelling trees still laden with leaves and the electricity network, Owen said Manitoba Hydro's work is far from over.

As of Tuesday morning, 12,500 customers remained without power — and it may take seven to 10 days in some areas for electricity to be restored. Each customer is a single billing location, which can represent multiple people living in a residence.

The public utility is requiring its line crews, who have been working 16-hour days to restore power, to remain on the job for the next 21 days.

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Employees were notified by Hydro they must cancel any previously booked vacations, and they'd be reimbursed for any plans they scrap.

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