Frederick County's utility agency says about 180,000 gallons of raw sewage overflowed into the Monocacy River during a rain storm earlier this week.
The agency says water from the heavy rain overwhelmed the pumps at the Ballenger Creek Wastewater Treatment plant south of the city.
Officials say the overflow didn't affect any downstream drinking water intakes.
Signs have been posted in the area advising people to avoid direct contact with the river.
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