UPDATE: Warning signs were removed on Friday, Jan. 12, after officials said water sample testing results showed that enterococci levels no longer exceeded advisory levels.

Stay out of the water at Ala Moana Regional Park.Health officials posted a warning after high levels of bacteria were detected in the water.

Levels of 1013 per 100 mL were detected during routine beach monitoring. The threshold level is 130 enterococci per 100 mL.

Health officials say they’re not sure what caused the levels to spike. There were no reports of any sewage spills at the time. Natural occurrences can also increase levels, such as land activity, or even a school of fish in the area where the sample is taken.

According to the alert, “testing for enterococci indicate that potentially harmful microorganisms such as bacteria, viruses, protozoa, or parasites may be present in the water. Swimming at beaches with pollution in the water may make you ill.”

Children, the elderly, and people with weakened immune systems are most likely to develop illnesses or infections after coming into contact with polluted water.

The most common illness is gastroenteritis. It occurs in a variety of forms that can have one or more of the following symptoms: nausea, vomiting, stomachache, diarrhea, headache or fever.

Other minor illnesses associated with swimming include ear, eye, nose and throat infections.

Health officials say while swimming-related illnesses can be unpleasant, they are usually not very serious. They require little or no treatment or get better quickly upon treatment, and have no long-term health effects.

Staff will be back at the beach Thursday to take another round of water samples with results expected Friday.

If levels return to normal, the signs will be removed.Click here for more information.