Shell Oil Co. has agreed to pay California $19.5 million over charges its gas stations violated environmental laws, Attorney General Jerry Brown said Friday.

Brown said his office and the California State Water Resources Control Board inspected more than 1,000 Shell stations during a three-year investigation, the Los Angeles Times reported.

"Shell Oil Co. disregarded the state's underground fuel storage and hazardous waste laws, committing hundreds of environmental violations at its gasoline stations across California," Brown said in a statement.

Along with paying the $19.5 million in penalties, Brown said, Shell must comply with state law and improve its spill monitoring, employee training and hazardous-waste management.