The city said it was notified by deputies that a break-in took place between 8 a.m. Monday and 4 p.m. Wednesday after someone sent police video the teens took of themselves climbing the water tower and then swimming in the water supply, KIRO-TV reported.
The video was posted on social media. In it, only one of the boys is seen swimming in the drinking water, but Snohomish police said they assume others took the same swim.
Snohomish police said five teenage boys were identified in the incident and charges will be filed, but they said who will be charged and what the charges will be have not been determined.
Coliform bacteria samples were collected at the tower and results have come back satisfactory, city officials said Thursday.
Officials said daily monitoring has been performed and things are within their normal range.
The North Zone Water Reservoir was isolated from the rest of the distribution system and will be flushed, officials said.
City officials said additional coliform samples are being collected and those results will be available Friday.
The city said it is working with the Washington State Department of Health Office of Drinking Water to review the situation and determine its next steps.