Updated at 1:09 p.m.

Wilsonville residents are safe to drink the tap water, according to test results released Monday.

City officials warned residents Friday that cyanotoxins, at trace amounts, had been detected in the drinking water. The cyanotoxins come from blue-green algae in the city's water source.

But laboratory testing of samples taken from the Willamette River, the treated water from the facility, and the drinking water found none contained microcystins, a dangerous cyanotoxin, according to a Monday update.

Salem, 30 miles south, spent last week mired in panic and controversy after officials there issued a water advisory that recommended some people avoid tap water because of cyanotoxins. Those groups were children younger than 6; the elderly; people on dialysis or with compromised immune systems; and pets.

Though the vast majority of residents were safe to drink tap water, the advisory still inspired a rush to buy bottled water that cleaned out grocery store shelves.

Salem officials also were criticized because they followed guidance laid out by the U.S. Environmental Protection Agency, which says vulnerable people can drink the water for 10 days before they risk illness.

But residents were unhappy that four days passed between detection of the toxins and the advisory being issued. The city gave the all-clear to drink the tap water on Saturday, five days after the city issued the advisory and three days after Gov. Kate Brown declared a state of emergency that authorized the Oregon National Guard to truck in drinking water to affected areas in Marion and Polk counties.

Wilsonville officials didn't expect to find unhealthy levels of cyanotoxins, but announced that some were found and that they would decide whether to issue an advisory Monday.

"We're being abundantly cautious here and providing information that allows our community members to make an informed decision," said Wilsonville City Manager Bryan Cosgrove.

The city's treatment plant was rebuilt in 2002 to include an ozonation system. Staff at the facility can infuse ozone into the water supply in an attempt to destroy microorganisms and degrade organic pollutants, such as cyanotoxins.

City officials will continue to test every day for seven days to be sure the levels stay below a dangerous threshold, said spokesman Bill Evans in a statement.

-- Molly Harbarger

mharbarger@oregonian.com

503-294-5923

@MollyHarbarger