The Tijuana Slough shoreline closed Sunday because of sewage contamination, San Diego County health officials said.
The closure affects the coastline at Tijuana Slough National Wildlife Refuge and Border Field State Park, the San Diego County Department of Environmental Health and Quality said.
The closure area includes all beaches from the International Border to the south end of Seacoast Drive.
Ocean currents were moving the sewage contamination north into the U.S. and water samples exceeded state health standards, officials said.
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Closure signs will stay in place until ocean water sampling meets state health standards for recreational use, the health agency said.