Authorities extended a water contact closure for the shoreline at Tijuana Slough National Wildlife Refuge and Border Field State Park north to Imperial Beach Sunday.
The new order by the San Diego County Department of Environmental Health and Quality includes the IB Pier.
Signs warning of sewage-contaminated water will remain in place until sampling results indicate the water is safe for recreational use.
The closure followed testing of ocean water samples that exceeded state health standards, from the border north to the IB shore.
Officials had warned Friday that the contaminated runoff may be moving north.