With the Pacific Coast Highway reopened in Los Angeles County, beachgoers visiting the area this holiday weekend are asked to avoid contact with ocean water around some Malibu and Santa Monica beaches.

As of Friday, the L.A. County Public Health Department has reported elevated bacteria levels from contaminated runoff in four L.A. County beach areas. Visitors should avoid swimming and surfing 100 yards up and down the coast from the Santa Monica Pier and the Pico-Kenter storm drain at Santa Monica Beach, near the Santa Monica South Tower 20.

Unsafe levels also have been detected 100 yards up and down the Castlerock Storm Drain at Topanga County Beach and Topanga Canyon Beach in Malibu.

Health officials say the presence of bacteria can increase significantly before and after rainstorms as polluted runoff flows into the ocean. Children, the elderly, and immunocompromised people are at higher risk of getting sick after coming into contact with contaminated ocean water.

In April, the Los Angeles County Department of Public Health lifted an Ocean Water Quality Advisory for beaches impacted by recent wildfires.

“Beachgoers may now enter the ocean water and recreate on the sand in these areas, but continue to be advised to stay away from fire debris as this may contain harmful substances and physical hazards, such as glass, metal debris, and sharp wooden debris. Residents are advised to continue following the Department of Public Health Ocean Water Advisories, which are non-fire related, and avoid entering the ocean water when ocean water quality exceeds State bacterial limits,” the health department said.

No warnings were issued for Long Beach and Orange County beaches.