A water contact closure was issued Wednesday for the ocean shoreline from the border to the south end of Seacoast Drive in Imperial Beach.
The San Diego County Department of Environmental Health and Quality said bacteria in ocean water samples exceeds state health standards.
Beaches in the area are frequently affected by sewage from Tijuana, and the county said the latest sewage-contaminated runoff may be moving north.
Water contact closure signs were placed at the affected areas and will remain until water sampling results meet state health standards for recreational use.
