More than 5,000 Sallal Water Association customers in the North Bend area will need to boil their drinking water until at least Oct. 1, the water district said Friday afternoon, a week after the presence of E. coli was first discovered in some water samples.

Results from 25 samples taken on Wednesday from throughout the water system showed five new hits of E. coli, including one from a well that is a source for the entire system, the Sallal Water Association said Friday. The association shut down the well Friday.

Sallal customers should bring all water to a full boil for one minute and then let it cool before drinking, brushing teeth, washing dishes or preparing food. The water can still be used for baths, showers and laundry.

Customers who purchase bottled water and have receipts will be reimbursed by Sallal after the advisory is lifted.

E. coli was first found in routine samples on Sept. 13, but those results didn’t come back from the lab until Monday. The entire system was placed on a boil advisory on Wednesday afternoon, the association said.

The two schools serviced by the Sallal water system, Opstad Elementary and Twin Falls Middle School, are operating on regular schedules but started using bottled water for drinking on Wednesday and boiling all water for food preparations, the Snoqualmie Valley School District said.

The water association has not found what caused the contamination, but it’s the second time in a year that the water supplier has issued a boil advisory. In November 2018, Sallal found that its water-tower tank had been contaminated with leaves, branches and debris. At the time, the association issued a “do not drink” order to 82 homes near the water tower and law-enforcement officials questioned a 14-year-old they say trespassed at the tower. The trespassing charges were forwarded to juvenile court.

City of North Bend water customers are not affected by the contamination.