California's top oil regulator is resigning after 17 months on the job, according to a newspaper report.
Steve Bohlen, the state's oil and gas chief, told the Sacramento Bee he is quitting to return to research.
The newspaper did not give a reason. The state's oil and gas division did not immediately return calls for comment.
The Associated Press reported earlier this month that Gov. Jerry Brown directed Bohlen in June 2014 to investigate and map out the oil and gas potential and history of the Brown family ranch.
Bohlen and Brown aides said the public work for Brown was legal and normal. The worker who prepared the map for Brown filed a whistleblower complaint, however, and former oil regulators told the AP the state oil work for Brown was unique.