Water quality officials have ordered ConocoPhillips to pay a $490,000 fine after toxic chemicals from one of its refineries washed into a section of San Francisco Bay.

The San Francisco Bay Regional Water Quality Control Board levied the fine after officials say chemicals from the oil giant's refinery in Rodeo spilled into San Pablo Bay seven times during a five-month period last year.

A state water official says toxic waste from the refinery's wastewater treatment system flowed into the bay during storms, killing thousands of tiny rainbow trout.

San Pablo Bay is a shallow estuary on the northern section of San Francisco Bay. It is a popular area for recreational fishing.

Officials with Houston-based ConocoPhillips say they're reviewing the complaint.