The Portland Water Bureau announced on Friday a boil water notice was put into effect after several tests showed E. coli contamination in the water.

According to The Oregonian, three tests done during a routine inspection of a couple Mt. Tabor reservoirs came back positive for E. coli. Water Bureau spokeswoman Jaymee Cuti said that the notice is in effect for about 670,000 residents.

Portland Water Bureau Administrator David Shaff said in a statement, "While we believe at this time that the potential health risk is relatively small, we take any contamination seriously and are taking every precaution to protect public health."

Any water that would be used for consumption in any way is advised to be boiled for no less than a minute, reports KPTV. Any drinks or ice still around that was made from water taken from the tap after May 20 should be tossed.

The boil notice will remain in effect until samples come back clean of E. coli and the affected reservoirs are currently offline. The PWB is currently looking into where the contamination could have originated.