PORTLAND -- It's safe to drink tap water on Portland's West side, but city officials still aren't sure what caused last weekend's E. coli scare.

Thousands of gallons of water were drained from Washington Park's Reservoir 3, and crews spent Monday using heavy-duty hoses to spray and clean out the reservoir. The reservoir holds about 16 million gallons of water.

One of the things that we did was, we had the staff go out and look for something obvious, like was there a dead duck floating around the reservoir?Something that you can point to and say, 'Aha, that must be it,' said David Shaff, Director of the Portland Water Bureau. Shaff said no obvious cause for the pair of positive E. coli tests was found.

City officials also reviewed surveillance tapes to see if there was any evidence of tampering with the water supply.

The water bureau issued a Boil Water Notice Saturday after a second positive test for bacterial contamination in Reservoir 3, located in Washington Park.

Background: Boil water notice issued for Portland's west side

The city issued an all clear Sunday morning after additional tests showed the water was safe.

Upstream and downstream tests conducted since the notice was issued were clear of contamination, Hall said Sunday.

West side water users were reminded to flush their water system to remove any potentially contaminated water from the plumbing. Click to see where faucet flushing is recommended

The risk of illness due to water contaminants was low, he said, but the notice was issued to protect customers. Drinking water regulations also required that notice be put in place.

Click for more from the Portland Water Bureau

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