Updated map of area affected by boil water alter. Courtesy California American Water

Customers of California American Water have been issued an advisory to boil water until at least Saturday night because of E. coli bacteria found in the drinking water supply.

The advisory, issued Thursday, affects approximately 17,000 water customers who reside in the city of Imperial Beach, Coronado south of Fiddlers Cove, and portions of San Diego and Chula Vista.

“Please be advised that the company is doing all it can to make sure water is of the highest quality and anticipate resolving the problem within 48-72 hours,” California American said in a statement.

External Affairs Manager Brian Barreto said the contaminated sample came from Imperial Beach and the cause is under investigation. He said that additional samples are being taken, and after two come back negative in a 48-hour period, the alert can be lifted.

He said the earliest that the water could be cleared for drinking is on Saturday night.

In the meantime, customers in the affected area were asked to use boiled tap water or bottled water for drinking and cooking purposes as a safety precaution.

The San Diego County Department of Environmental Health ordered restaurants in the affected area to immediately cease operations. “It is unsafe to prepare food, wash dishes, hands, etc. in E. coli contaminated water,” the department said.

In addition, schools in one district will keep their doors closed Friday due to this advisory but another district will keep their schools open.

All schools in the San Ysidro School District will be closed, including San Ysidro Middle School, Vista Del Mar Middle School, La Mirada Elementary School, Ocean View Hills Elementary School, Smythe Elementary School, Sunset Elementary School and Willow Elementary School.

But the Chula Vista Elementary School District says it’s aware of the advisory and will keep all of their schools open and will be taking precautionary measures to ensure the safety of students and staff.

These measures include turning off the water (excluding the toilets). They will also provide water bottles, hand sanitizer, and portable hand washing stations. Also, all food items served Friday will not need to be rinsed or washed, the district explained.

California American Water customers were also asked to immediately discontinue any non-essential water usage, including all outdoor irrigation.

Customers with questions can call California American Water’s customer service center at 888-237-1333. Bottled water is available free to affected residents at the company’s operations center at 1025 Palm Avenue, and officials are planning to set up two more distribution locations.

The Otay Water District posted on the social media platform X, formerly known as Twitter, letting its customers know it was safe to consume its water.

“Otay Water District customers are NOT under a water boil alert. Otay water continues 2b safe to use & drink. Cal American Water Company issued a boil water notice to its customers. It does NOT affect Otay customers,” the agency post reads.

Updated at 11:45 a.m. on

City News Service contributed to this article.