E. Coli was discovered in the water system at Lake Morena County Park and visitors should not use the water without boiling it first, county health officials warned.

A boil water order was issued Thursday for the camping and fishing park located in Campo, about 50 miles east of San Diego, due to a positive test for E. Coli bacteria, the Department of Environmental Health (DEH) said.

The bacteria was found in the park's drinking water system, which provides water for the camping and RV sites, cabins, public restrooms and showers.

The agency said the water should not be used without boiling it first, which ensures it is clear of all bacterial contamination.

Ingesting E. Coli can cause diarrhea, cramps, nausea, headaches or other symptoms and is especially dangerous for infants, young children, elderly people and those with weak immune systems, DEH said.

The boil water order was in effect indefinitely. DEH would clear the order once their lab tests confirm there is no presence of bacteria in the water.

Lake Morena is a popular spot for hikers because of its close proximity to the Pacific Crest Trail. It is also common among fishers because of the variety of freshwater fish that fill the reservoir.