The Jackson County Forestry and Parks Administration says Lake Wazee Beach will remain closed through the weekend.
This following a mysterious illness which sickened over 170 people who swam in the lake over the 4th of July holiday.
Testing of lake water by the USDA has not proven any conclusive organism is the cause.
Markers for fecal contaminants have been found to be present in the beach water.
Flu-like symptoms including vomiting, diarreah, and body aches have usually subsided in 24-36 hours, according to Jackson County Health Officer Christine Hovell.
Officials are hoping that by closing the beach, natural elements such as warm weather and UV lighting from the sun will destroy human contaminants in the water.