(California News Service) Gas bills jumped by hundreds of dollars over the past few months for many Californians - and Tuesday, the California Public Utilities Commission held a hearing to find out why. 

Some of the reasons cited - high demand during cold weather, and the failure of utilities to store enough gas for the winter or hedge against problems with interstate pipelines. 

Heidi Harmon, former mayor of San Luis Obispo, applauds Governor Gavin Newsom's call for a federal investigation into possible market manipulation.

"Why did gas prices go up so much, in such a short period of time?" asked Harmon. "What's really going on there? And what is the remedy, and who needs to be held accountable?"

Prices are now coming down, but the CPUC said the price of natural gas on the West coast peaked in December - at eight times what people in the Southeastern U.S. were paying. 

The agency voted to accelerate a tax credit for millions of Californians that will take $90 to $120 off their gas bills in March.

Dominic Frongillo, executive director and co-founder of the group Elected Officials to Protect America, said he is convinced that the best way to protect people's pocketbooks and the climate - is to transition away from oil and natural gas.

"The fossil fuel industry's volatility - and collusion, in many cases - is causing prices to spike," said Frongillo. "And the only way to end this is to accelerate our transition to 100% clean energy."

More than 440 California elected officials have signed an open letter to the governor, asking for a plan to phase out oil-and-gas production in the state.