On Tuesday, Wake County officials closed the beach, but they say other areas of Falls Lake are not affected.
The EPA checks bacteria levels in the water weekly during the summer to cut back on the number of illnesses.
Officials must sample water at the acceptable levels for two consecutive days before they can confirm the water is safe for swimmers.
Just five days ago, a similar problem popped up at Lake Wheeler. Now the high levels of bacteria are gone and Lake Wheeler beach is back open.
Before heading out to swimming areas, the county suggests calling the recreational lake facilities to find out if they are open for swimming.
Also, to prevent recreational water illness the county suggests washing hands with soap and water and thoroughly showering after swimming, tubing or skiing in recreational lakes.