Updated at 5:40 p.m.

Salem residents got the all-clear Saturday to drink the tap water, five days after the city issued an advisory and eight days after a low-level toxin was detected.

Though the water posed little threat to most people, officials said traces of cyanotoxins found in the city's water supply could potentially sicken young children, people with compromised immune systems, pregnant women and others.

Mayor Chuck Bennett publicly thanked Salem area residents who helped neighbors and shared water. He also said the city will continue to post water data on its website and work to hone its response to future algae blooms, the source of the toxins.

"As algal blooms are a natural process, the possibility does exist that an advisory could go into effect if health advisory levels return," Mayor Chuck Bennett said in a prepared statement. "While we hope this is not the case, we have learned many difficult lessons that will help all of us be bettered prepared to manage the situation."

City officials issued the health advisory Tuesday, prompting a run on bottled water that quickly cleaned out area grocery stores. Two days later, Gov. Kate Brown declared a state of emergency for Marion and Polk counties, opening the door for Oregon National Guard troops to truck in drinking water to the affected areas.

Those water fill stations will be open until 6 p.m. Saturday. Residents who fall into any of the advisory categories are being encouraged to run their faucets for a few minutes before drinking any tap water, to ensure all toxins are flushed out.

Water samples collected Wednesday and Thursday tested clean, city officials said in a news release Saturday. The toxins were caused by algae blooms found last week in the Detroit Reservoir, which supplies water to the cities of Salem and Turner, as well as the Suburban East Salem Water District and Orchard Heights Water Association.

The city took some heat over its initial handling of the situation. The Oregon Office of Emergency Management declared a civil emergency via text alert in Marion, Clackamas, Benton, Deschutes and Yamhill counties and advised residents to prepare for action. Cities and police agencies in those areas were then compelled to assure residents there was no civil emergency and urge them not to call 911.

Cory Grogan, a spokesman for the emergency management office, told The Oregonian/OregonLive the alert was sent on behalf of the city of Salem. He said he didn't know why the alert was treated as a civil emergency or why it went out to people outside the affected areas. Salem officials then apologized for panicking residents.

"I regret that the initial water advisory and the city's communication about the water advisory had the widespread impact that have occurred for the past 60 hours," Salem City Manager Steve Powers said Friday during a news conference. "We were trying to achieve the exact opposite -- maintaining confidence in our water system and our water."

Though algae blooms are a relatively new problem in the Pacific Northwest, the spread of the cyanotoxins they release is a growing issue across the country.

Dave Emme, who manages the Oregon Health Authority's drinking water program, told The Oregonian/OregonLive this week that the U.S. Environmental Protection Agency doesn't yet regulate cyanotoxins -- a process that typically requires years of testing and analysis. So when Salem officials contacted the EPA and Oregon Health Authority to consult about their tap water, the three agencies had to figure out their protocol on the fly.

While the issue is resolved for now in Salem, the residents of Wilsonville and nearby Sherwood are waiting to hear whether the cyanotoxins detected Friday in their water, which is drawn from the Willamette River, would require a health advisory. Officials are expected to have an answer on Monday.

-- Molly Harbarger

mharbarger@oregonian.com

503-294-5923

@MollyHarbarger