FAIRVIEW, Ore. -- After another round of bacteria tests at Blue Lake came back negative for E.coli, scientists now suspect the swimmers who got sick this week were infected with the norovirus, according to Laura Odom, spokeswoman for Metro.
The lake's swimming area remained closed on Tuesday.
Scientists sample and test the lake's water twice a week.
We invited a private water quality expert to test the water in an independent lab.
Beth Myers, owner of Waterlab Corporation in Salem, said bacteria would spread easily in Blue Lake since the water does not have a swift current.
"That's the problem with swimming areas in open water," said Myers. "If this were a stream, it would be different."
Oregon has so many swimming areas that fall under different authorities and government agencies. Some are tested. Some are not.
The city of Portland tests the water in swimming pools and fountains as well as some spots along the Wilammette River.
Some ocean beaches are tested by the state thanks to funding from the federal government, while some beaches are not tested.
Washington County tests 25 spots along the Tualatin River.