The burned remains of a vehicle and home are seen during the Camp fire in Paradise, California on November 8, 2018.

Shares of utility PG&E popped 37.5 percent on Friday after the head of a regulator eased worries about the California-based utility going bankrupt. Friday's rise marks the stock's biggest in at least four decades.

In a call with Wall Street analysts, California Public Utilities Commission head Michael Picker reportedly said he could not imagine letting PG&E go bankrupt as it faces billions of dollars in potential liability from the wildfires ravaging California. Picker's comments on the call were first reported by Bloomberg News.

Picker later told the San Francisco Chronicle that the agency would implement a provision through which utilities can pass wildfire costs on to consumers.

"Why is the CPUC stepping up now vs. mostly looking for legislative initiatives earlier? Given the reaction in the stock market, we think there was an appropriate level of urgency that something needed to be done," an analyst at Citi Research wrote in a note Friday. The analyst also upgraded the stock to buy from neutral.

"We also think the CPUC is stepping up now because it is easier for them to come out quickly to support the utility vs. something from the political spectrum," the note said.

PG&E's stock had sunk more than 50 percent for the week entering Friday's session amid concerns that its equipment could be partly responsible for the so-called Camp Fire raging in Northern California. The stock ended the week down 38.9 percent.