BENNINGTON -- Local power was restored quickly after a failure at Green Mountain Power's Benmont Avenue substation, but the company isn't taking any chances.

"There was a failure inside a piece of enclosed switch gear," said GMP spokeswoman Dorothy Schnure. While the company was able to restore power before completing the repair, a portable substation was brought in to serve as backup in case of need. So far, there has been no need, Schnure said, but the backup will be left on-site for a time anyway.

People living in proximity to the station heard a loud bang at about 6:50 a.m. Sunday, heralding the loss of electricity to approximately 800 local power customers. Outage times ranged from only a couple of minutes to roughly an hour, according to comments given on the Banner's Facebook page.

Workers swarmed the substation all day and far into the night Sunday, working well past midnight to fix the problem. "We were able to fix the switch gear, but we're leaving the portable substation there for a while, just in case," Schnure said.

She added that northern Vermont GMP customers are presently having a much harder time, as they haven't experenced the warm weather that the south has had. "The ice is not melting off the trees," she said. "It keeps building up, and there will be outages still for several days."

The Vermont Division of Emergency Management and Homeland Security reported that as of Sunday morning, some 15,000 Vermonters had lost power, most of them due to ice buildup and freezing rain. Many were still without power Monday. GMP reported about 5,700 outages, and Vermont Electric Cooperative, more than 9,000, due to the storm.

All of GMP's crews are working on outages, and the company has engaged 400 contractor lineworkers and tree-trimmers from out of state, enabling them to work on their own outages and share workers with other utilities in Vermont who need the help. And need it they do. "A lot of people get their power knocked out, get it back on, and it goes back out," she said.

The Vermont Department of Health also reported a spike in carbon monoxide poisoning, as people turned to generators and other heat sources. Department officials warned people to use caution, to refrain from using generators, charcoal grills or hibachis inside, and to clear the vents on any gas appliances being used outdoors. Early symptoms of carbon monoxide poisoning include dizziness, headaches, and nausea.

The Associated Press contributed to this story.

Reach Stephanie L. Ryan at sryan@benningtonbanner.com, or follow her on Twitter @StefkaRyan