A boil water advisory was issued Wednesday night for the entire District of Columbia and neighboring Arlington County due to a spike in algae blooms in the Potomac River, officials said.

The District of Columbia Water and Sewer Authority said the advisory, which it described as “precautionary,” also included the Pentagon, Arlington National Cemetery and Reagan National Airport.

“We have no information that the water was contaminated by this incident, but we issue this advisory as a precaution while we test the water,” the agency said.

The Washington Aqueduct is sourced by the Potomac River and serves as the public water supply for about one million people in the D.C. area, Arlington County and other portions of Northern Virginia.

The U.S. Army Corps of Engineers said in a news release that the advisory stemmed from “elevated turbidity levels in the water supply caused by increases in algae blooms in the Potomac River.”

Turbidity is a measure of the clarity and cloudiness of water.  

“Customers may notice their water looks cloudy or hazy,” Arlington County said in a news release.

The Washington Aqueduct has two water treatment plants. The Army Corps of Engineers responded to the elevated turbidity by temporarily transferring all water treatment operations from the Dalecarlia plant to the McMillan plant, DC Water said.

The Environmental Protection Agency also authorized adding additional copper sulfate and sodium permanganate to the aqueduct’s reservoirs to combat the algae, the Army Corps of Engineers said.

Residents were advised to bring drinking water to a rolling boil for one minute before letting it cool. Water should then be stored in a covered container.

The advisory will remain in effect until further testing deems the water safe to drink.