Crews working to restore power to patches of downtown Portland after a cable failure in an underground vault knocked out service to about 100 customers say they won't finish in time for the Monday morning commute.

Steve Corson, a spokesman for Portland General Electric, said crews have been working throughout the day and expect to get some customers back on line Sunday night.

"There will be some customers without power probably until midday tomorrow," Corson said.

Drivers who travel through downtown Portland should expect slower-than-average commute times Monday morning. Traffic lights at on Southwest Fifth and Sixth Avenues at Broadway, Taylor, Alder, Yamhill and Washington streets are off, and four-way stop signs are filling in to direct traffic.

Corson said it's unclear what caused the cable failure, but the weather isn't a likely culprit.

"Wires go bad," he said.

The outage is contained in the core downtown area, including the US Bank Tower and part of Pioneer Place mall.

--Kelly House