SAN FRANCISCO, US (AFP) - Shell Oil Company will pay California more than US$19 million (S$26.6 million) because of environmental violations at service stations throughout the state, officials said.

The agreement, filed Friday in a California state court, requires Shell to pay US$17.8 million in civil penalties as well as US$1.7 million in costs to state and local agencies.

The deal ends a three-year investigation into more than 1,000 Shell stations throughout the state focusing on operation and maintenance of underground storage tanks, as well as the handling of hazardous waste materials.

California Attorney General Jerry Brown said in a news release that the investigation found hundreds of violations at the company's gasoline stations in California.

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

Shell released a statement saying it already was working to fix the problems with its underground storage tanks, or USTs.

"While admitting no liability, Shell is pleased to reach this settlement and has been working cooperatively with the state of California since 2006 to resolve this matter," said the statement attributed to Shell spokesperson Alison Chassin.

"We are proud of the great strides we have made to improve our UST operations, and in fact many of the measures outlined in the settlement are actions that Shell has already implemented.

Shell, which is based in The Hague, Netherlands, has about 102,000 employees in more than 100 countries worldwide.

Under the terms of Friday's deal, Shell agreed to take immediate steps to improve spill and alarm monitoring, employee training, hazardous waste management and emergency response at its gasoline stations.