A new study says roughly 20 percent of California's oil production now comes through hydraulic fracturing.
The study was carried out by the California Council on Science and Technology. It's the first of several reports commissioned by the state as California sets up regulations for fracking.
Future studies will look at the environmental impact of fracking. Wednesday's report noted that roughly half of the 300 wells drilled in the state each month involve fracking.
Fracking involves forcing fluids, sand and chemical underground to break rock formations and extract oil and gas.
Environmental groups on Wednesday criticized state oil and gas regulators for moving forward on their own fracking review without waiting for the independent reports.