More than 9,000 people were without power in Multnomah County on Monday morning.
Portland General Electric's website said equipment failure was the cause of at least seven different outages. At 8 a.m., 9,138 customers were affected.
A PGE spokesperson initially said the situation appeared to be linked to the heat wave. It was later discovered a squirrel had gotten into a substation and caused the outages.
The power is expected to be restored for most customers by 10 a.m.
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