RIDGEWOOD, N.J. (CBSNewYork) — Three New Jersey towns are under a boil water advisory after traces of fecal E. coli was found in a groundwater sample during a routine test.

Ridgewood Water issued the advisory for portions of Ridgewood, Wyckoff and all of Glen Rock.

The advisory comes after a sample earlier this week from a raw groundwater source tested positive for E. coli before any treatment.

“One of our well water samples in one of our wells tested positive for E. coli,” Richard Calbi, director of operations for Ridgewood Water, said. “The water was subsequently treated, but as a result we’re required to do a tier one notification to the public.”

Ingesting fecal E. coli can make you sick. Symptoms include vomiting, diarrhea, cramps and headaches. It may pose a special health risk for infants, young children, the elderly and those with severely compromised immune systems.

So far, no cases of illness have been reported.

Ridgewood Water said boiled or bottled water should be used for drinking, cooking, ice, brushing teeth, washing dishes and any other food preparation until further notice. It said water should boil for one minute and allowed to cool before using.

While some stores shuttered their doors, others stocked up on bottled water and took extra precautions.

“The cook has to boil some water to make sure everything is OK,” John Galianos of the Daily Treat restaurant told CBS2’s Magdalena Doris. “Just make sure everybody is safe make sure we don’t give anybody water and that’s it.”

Parents have also been notified. The Glen Rock School District tweeted out a message Wednesday saying students should bring bottled water to school on Thursday.

The water company said the sample that tested positive was treated before reaching the public and the well has since been shut off and disinfected.

Ridgewod Water is now working with the state.

“They are requiring that nine additional samples in our distribution system,”┬áCalbi said. “That testing is currently going on.”

The company said it will notify customers when the boil water advisory is no longer in effect, which it anticipates to happen by Friday.

For more information, contact Ridgewood Water at 201-670-5520. For general guidelines on ways to lessen the risk of infection by microbes, contact the EPA Safe Drinking Water Hotline at 1-800-426-4791.