The suit filed Tuesday in state court in California accuses the utility of failing to maintain its infrastructure and properly inspect and manage its power transmission lines.
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The utility's president said earlier the company doesn't know what caused the fire, but is cooperating with the investigation by state agencies.
An email to PG&E about the lawsuit was not immediately returned.
PG&E told state regulators last week that it experienced a problem with a transmission line in the area of the fire just before the blaze erupted.
A landowner near where the blaze began said PG&E notified her the day before the wildfire that crews needed to come onto her property because some wires were sparking.
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Shares in PG&E are trading at their lowest level in more than a decade.
Shares in the San Francisco company plunged another 31 percent Wednesday, to $25.99. The have lost about 45 percent of their value since last week.
PG&E told state regulators last week that it experienced a problem on a transmission line just before the blaze erupted in the vicinity.
Investigators have not determined the cause of the blaze.