PG&E said liabilities related to the wildfire ravaging northern California could exceed its recently renewed insurance cover if its equipment was found responsible for starting the Camp Fire.

Shares in California's largest public utility plunged nearly 22 percent on Wednesday, and have lost nearly half of their value since the fire began last week.

Seth Klarman's $30 billion Baupost Group raised its exposure by 321 percent during the third quarter to own 18.9 million shares at the end of September, according to regulatory filings and data from Symmetric.io.

Viking Global Investors put on a new position buying 5.7 million shares during the quarter. BlueMountain Capital bought 4.1 million shares to own 4.3 million at the end of the quarter. Appaloosa Management raised its exposure by 122 percent to own 3.9 million shares at the end of September.

A number of hedge funds that sometimes make bets on distressed investments had been moving into PG&E after deadly fires last year.

Even before the Camp Fire began this year, PG&E was facing some 200 lawsuits on behalf of 2,700 plaintiffs stemming from last year's fires. Some of last year's fires were caused by trees toppling into or making contact with PG&E power lines.

While the cause of this year's fire is still under investigation, the company told regulators they had experienced equipment problems in areas around the time the fire was first reported.

The funds all declined to comment on their investments.

(Reporting by Svea Herbst-Bayliss; Editing by Chris Reese)