Rock County Environmental Health Director Tim Banwell is watching the local swimming holes closely after blue-green algae was discovered in nearby Delavan Lake. Banwell says the health department took samples from area waters Tuesday and no dangerous algae was observed in Rock County. He says test results for E-coli and other selected contaminants should be back as early as Thursday. The DNR urges swimmers, boaters, and other recreational users to avoid contact with water where algae is present. When ingested, the algae can produce harmful toxins in people and pets.