The letters ‘KKK,' were sprayed painted in blue paint on the base of the National Fire Dog Monument, which stands on 5th and F Streets NW. Blue spray paint also marked the statue of the dog's head.
A photo of the graffiti was posted to the National Fire Dog Monument "Ashes to Answers" Facebook page.
Work to remove the paint is underway, and D.C police are investigating.
In a statement, the D.C. Firefighters Association said large piles of trash were also dumped in the back parking lot of the firehouse, which is located at 500 7th Street NW.