Washington — Markings appeared on the National Mall in Washington, D.C., on Thursday that seem to depict the numbers "86 47," according to photos taken from the top of the Washington Monument.

A photographer for the Reuters news outlet saw the apparent markings just before federal authorities arrived to look into the incident, according to the wire service. Photos taken by the Reuters photographer show the faint tracings of "86 47" in the grass with the World War II Memorial in the background.

The "8" appears most prominently, while the "6" and "7" can be seen less clearly. The number "4" is the least visible in the photos. It was not immediately clear how the markings were made or who made them. 

The U.S. Park Police said, "At approximately 11:30 a.m., U.S. Park Police responded to a report of vandalism of the west lawn of the Washington Monument. The numbers '8647' were marked in the grass. The cause of the discoloration has not yet been determined. Grass samples have been collected for testing. The investigation is ongoing."

A spokesperson for the Interior Department said, "The deranged vandalism on our National Mall will not be tolerated. Any threat against the President is taken very seriously by the Department, and our U.S. Park Police will investigate this incident and hold those responsible accountable." 

"Anyone who engages in or endorses political violence or assassination culture must be condemned in the harshest terms possible," White House spokesperson Davis Ingle told CBS News in a statement in response to the markings. "They should also immediately seek psychiatric help to treat their severe and debilitating case of Trump Derangement Syndrome that has warped their brains and made them sick in the head."

The term "86" is slang meaning to "throw out" or "get rid of," according to Merriam-Webster. The phrase is commonly used in restaurant kitchens and originated at soda counters in the 1930s, according to the dictionary. But the term gained more attention recently when former FBI Director James Comey was indicted after sharing an Instagram post last year that showed seashells on the beach arranged to form "86 47."

Comey deleted the post and said he believed the shell formation was communicating a "political message." The former FBI chief said he did not realize that some people associate the numbers with violence. 

Comey was charged with two counts of making threats against President Trump. He has not yet entered a plea and is set to be arraigned in New Bern, North Carolina, in late September. 

Mr. Trump has said the term "86" is a mob term that connotes violence and, when paired with "47," means "kill President Trump." Mr. Trump is the 47th president. 

"EIGHT MILES OUT, SIX FEET DOWN!" he wrote on Truth Social in April.

Dubbed "America's Front Yard," the National Mall stretches from the Lincoln Memorial to the west and the U.S. Capitol to the east. It is set to be the site of several events honoring the nation's 250th anniversary.