SACRAMENTO, Calif. (AP) — California Gov. Gavin Newsom cracked down on oil producers Tuesday, halting approval of hundreds of fracking permits until independent scientists can review them and temporarily banning another drilling method that regulators believe is linked to one of the largest spills in state history.

The state Division of Oil, Gas and Geothermal Resources announced it will not approve new wells that use high-pressure steam to extract oil from underground. It’s the type of process Chevron uses at an oil field in the Central Valley that leaked more than 1.3 million gallons (4.9 million liters) of oil and water this summer.

That process is different from fracking, which uses water and other chemicals at high pressure to extract oil. California has 263 pending fracking permits but has not approved any of them since July. That’s when Newsom fired California’s top oil and gas regulator after learning the state had increased fracking permits by 35% since he took office in January, angering environmental groups.

Newsom, a Democrat, called the crackdown necessary to strengthen the state’s oversight of oil and gas extraction “as we phase out our dependence on fossil fuels and focus on clean energy sources.”

“This transition cannot happen overnight; it must advance in a deliberate way to protect people, our environment and our economy,” Newsom said.

California has been a leader on environmental issues, with Newsom’s Democratic predecessor, Jerry Brown, making climate change his signature effort. Brown was criticized for failing to ban fracking or oil drilling, arguing that the state needed to tackle demand before moving on to supply.

The oil industry called Newsom’s changes “disappointing,” with the Western States Petroleum Association saying California’s environmental regulations already lead the world.

“Every barrel delayed or not produced in this state will only increase imports from more costly foreign sources that do not share our environmental safety standards,” group president Catherine Reheis-Boyd.

California is one of the top five states for oil production, producing more than 161 million barrels last year. Fracking occurs in some of the state’s largest oil fields, mostly in the Central Valley.

The steam method is less prevalent but accounted for 8 million barrels of the state’s oil production in 2018, according to the Department of Conservation. But regulators believe it is linked to the oil spill at a Chevron well that began in May.

By Adam Beam