Monterey County health officials have posted an advisory at Lover’s Point Beach and Monterey Municipal Beach due to fecal contamination.
Officials said samples taken on Monday showed high levels of indicator bacteria, which are used to test for fecal contamination.
Visitors are asked to avoid swimming or making contact with the water, as it can potentially cause illness.
Possible sources of the fecal contamination include marine life and other animals, storm drains and human activity, according to the health department.
Rainfall can also be associated with increased bacteria, especially in areas near man-made and natural storm drains, health officials said.
The advisory will be lifted once samples show safe levels of bacteria for recreational activities.