A citywide boil notice was issued for Portland, Oregon, after state health officials detected E. coli in the water supply.

The Portland Water Bureau said Friday that residents should boil all tap water used for drinking, food preparation, tooth brushing and ice for at least one minute. Ice or any beverages prepared with un-boiled tap water on or after Tuesday should be dumped.

The notice, which also covers some suburban cities, affects about 670,000 people. It will remain in effect until tests show the water system is clean.

The samples that tested positive for bacteria were collected this week from two uncovered reservoirs at Mount Tabor. The Water Bureau said it collects about 240 bacterial samples per month throughout the system, and the test to determine the presence of bacteria takes 18 hours.