"I'm seeing progress," Newsom said on a visit to the Cymric oil field, where the oil and water are contained in a dry desert creekbed. The leaks are known as surface expressions, which can be caused by injecting steam into the ground.
Chevron uses steam injection to extract oil in the Cymric field. The steam softens the thick crude so it can flow more readily. It is a different process from fracking, which breaks up underground layers of rock.
Still, Newsom told reporters the state would ask Chevron to turn over data so regulators can investigate the cause of the spill.
"The lesson learned here is we've got to be aggressive on monitoring," Newsom said.
"We've got to hold folks to account. And I think Chevron ... are being forthright and recognizing they need to be held to account. They need to mitigate. They need to clean this thing up. They are taking it seriously, at least based upon my interactions. But we'll analyze that and we're going to request their data. We're not just going to assume things."
The company has said the initial leak began May 10 after its crews tried to seal off a damaged and abandoned well.