After being open for only one week, officials closed the shoreline near the border again Sunday because of sewage contamination.
The closure affects all of the shoreline at Tijuana Slough National Wildlife Refuge and Border Field State Park, officials said Sunday.
Ocean water samples exceeded state health standards, according to the San Diego County Department of Environmental Health and Quality.
The closure includes all beaches from the international border to the south end of Seacoast Drive in Imperial Beach. Closure signs will remain in place until sampling results meet state health standards for recreational use.
Just last Saturday, officials lifted a water contact closure after testing showed the ocean water was safe for recreational use. A water contact closure was issued June 24.
The Tijuana River enters San Diego County from Mexico and flows through the southernmost part of the county before it empties into the Pacific Ocean.
Sewage-contaminated runoff that enters the river in Mexico may be moving north along the shoreline, according to a June statement from the health agency.
Border-area beaches have been closed off and on all year.