SAN DIEGO — About 350 East County residents have been ordered to boil their water before using it for cooking or drinking after traces of E. coli were found in a system in Julian, county officials said Saturday.

Authorities got a positive test for bacteria in the Butterfield Ranch mobile home and recreational vehicle community’s water and believe it could be contaminated with human or animal waste, the county’s Department of Environmental Health and Quality said.

The system serves a population of roughly 350, according to California government records. Located on Great Southern Overland in Julian, a county spokesperson said it includes 75 mobile home spaces, 233 RV spaces, an office with a store, a clubhouse and three swimming pools.

The bacteria may pose an increased health risk for infants, young children, some elderly, and people with severely compromised immune systems.

County health officials say residents should bring water to a boil, let it boil at least one minute, and then let it cool before using it to drink or cook with. Taking showers, bathing and washing hands, laundry and dishes are still permitted. Read more on the region’s FAQ.

Symptoms of E. coli infection include severe stomach cramps, diarrhea (often bloody), and vomiting, according to the Centers for Disease Control and Prevention.

Residents were told to call Kyle Newman, Butterfield Ranch Community supervisor, at 760-267-3657 with questions.

City News service contributed to this report.