LONG BEACH (AP) — Power was restored to most of downtown Long Beach and the power network appeared to be holding well Saturday, three days after underground electrical fires prompted outages that affected thousands of customers.

Southern California Edison said it’s still troubleshooting the system and monitoring voltage levels. About 200 customers in several isolated areas are still without power, it said.

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Fires in three electrical vaults short-circuited a power grid Wednesday afternoon and darkened numerous traffic lights in the city of 469,000. The fires were quickly doused, and no one was hurt. Power was restored to some by portable generators. But same areas remained dark through Saturday morning.

The utility said all customers may still experience intermittent outages.

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City officials were providing shelter and handing out food, flashlights, ice and water. They opened a shelter in Cesar Chavez Park’s community center that included a cellphone charging station, hot showers and a place to stay, although pets were not allowed.

“We’re reminding people that an unlit traffic light should be treated as a four-way stop sign, and people should be cautious walking and driving,” said Rachel Tanner of the Long Beach City Manager’s Office.

The cause of the fire and subsequent outage hasn’t been determined.

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