PORTLAND, Ore. (AP) — More than 50,000 customers remained without power Saturday, more than a week after an ice storm ravaged the electrical grid in greater Portland, Oregon.

Portland General Electric had hoped to have power back to all but 15,000 customers by Friday night but discovered additional damage Friday after it reached previously inaccessible areas, the utility said in a statement Saturday.

The worst ice storm in 40 years knocked out power to more than 350,000 residents at its peak and killed five people, including four who died from carbon monoxide poisoning as they tried to stay warm. A layer of ice an inch thick coated power lines and trees, adding 1,000 pounds of extra weight to each span of wire from pole to pole, PGE said.

Oregon National Guard troops called up by Gov. Kate Brown began welfare checks in Clackamas County on Saturday and were expected to begin the same checks in Marion County, to the south, on Monday.

Those who still don’t have power live mostly in rural areas to the south and east of Portland.

“We know how frustrating this is, as we’ve discovered even more challenges to getting our repair and restoration work done along the way. Our 350 crews and the staff who support them will not stop working night and day until we have the power back on for every single customer,” said Larry Bekkedahl, the utility’s vice president of grid architecture, integration and systems operation.

The damage and dangerous conditions left behind by the storm, which came in three waves starting Feb. 12, is the worst in the history of Portland General Electric, CEO Maria Pope said. Crews were not able to safely enter the worst-hit areas for 48 hours because trees laden down with hundreds of pounds of ice were falling constantly, the utility said.

One-quarter of customers lost power multiple times over the course of the three-day storm as ice-laden trees fell on lines.

Even now, progress is slow because of “widow-maker” branches and trees dangling high above downed power lines. Seventy-five timber crews are working alongside utility crews to remove the trees before work can begin on restoring the power grid.

Crews have repaired 330 miles of power lines and “with every mile, we find additional damage,” Bekkedahl said.

Pacific Power, another utility provider in the area, said Friday it had restored power to 98% of the 80,000 its customers who lost power and was working individually with about 1,300 customers to restore power.

Updates on power outages are available here.

A high school in Oregon City remained Saturday to provide residents without power with charging stations, flashlights, batteries, blankets, food and warm showers.