New tests show the water going to a group of businesses near Lemmon Drive and US 395 is safe.
The Washoe County District Health Department required food-serving businesses in the area to close Friday, after a contaminant was found in water. An advisory to boil water was also issued for businesses that remained open.
Only businesses were believed to be affected by the contamination.
Health officials have now identified the contaminant as coliform bacteria. E. coli is a type of coliform, but it's not known if that was the type in the water.
Officials say no one is known to have become sickened in the incident.
The District Health Department says a routine monthly test revealed the contamination. However, officials say the water system was flushed with clean water and two tests showed the water is now safe to be used.
Water Resources says the contamination may have been related to road construction occurring near pipes.
Businesses were required to run their water for a certain amount of time and exercise other precautions before they could open again.