Ontario's provincial utility says power has been restored to more than half a million customers four days after an ice storm first moved into the region, but that some hard-hit areas may remain without it until the end of the week.

Over 300,000 Canadians faced power outages in parts of Ontario on Sunday as an ice storm pummeled the region over the weekend, according to electricity provider Hydro One.

Chris Deathe, district manager for Davey Tree Expert’s Hamilton branch, said 38 of the company’s crews were dispatched to heavily impacted areas north of Toronto, including Bracebridge, Peterborough, the Kawarthas, Barrie and Orillia, to deal with extensive ice storm damage. Crews have encountered downed trees and power lines.