Those heading to the beach this week are advised to stay out of the water as several beaches are under advisory for excessive bacteria levels.

Eight beach areas have been placed under warnings for high bacteria levels by the Los Angeles County Public Health Department.

These areas are under advisory, which means the “ocean’s water bacteria levels exceed state standards and may cause illness.” Those with weakened immune systems, along with children and the elderly, are most at risk officials said.

Beach areas affected by the warnings:

-Malibu Point at Surfrider Beach near Malibu Tower 3
-Santa Monica Pier in Santa Monica
-Mother’s Beach in Marina Del Rey
-40th Street extension in Manhattan Beach
-Manhattan Beach Pier in Manhattan Beach
-Hermosa Beach Pier in Hermosa Beach
-Redondo Beach Pier in Redondo Beach
-Redondo Beach at Sapphire Street

The closure of an area near the southern tip of Torrance Beach earlier this month was lifted on Thursday after recent samples “identified water quality levels within state standards.”

The exact cause of the heightened bacteria is not known, but officials say runoffs from rainstorms can also contaminate waters. If heavy rainfall occurs, it’s typically advised to stay out of ocean waters, rivers, creeks or flowing drains for at least three days after a storm.

Beach waters are tested every week throughout the year to ensure the most up-to-date bacteria levels. An interactive map on the L.A. Public Health Department site offers the most up-to-date beach warnings and closures.