IMPERIAL BEACH -

A stretch of the South County shoreline has been closed off to swimmers because bacteria levels from sewage-contaminated runoff originating near the U.S.-Mexico border exceed state standards, county health officials said.

Recent rainfall has pushed sewage-contaminated runoff from the Tijuana River into the Tijuana Estuary, and water samples confirmed that bacteria levels were elevated above state standards in Imperial Beach, according to the county Department of Environmental Health.

Authorities expanded the existing water contact closure at the Tijuana Slough National Wildlife Refuge shoreline north to include Imperial Beach, including Camp Surf, according to a statement from the county agency.

Signs warning of the contamination were placed in the area and will remain up until field measurements indicate the ocean water is safe for recreational use once again, according to the Department of Environmental Health.