Police investigate '8647' written in grass on US national mall

US police are investigating a large imprint of the numbers 8-6-4-7 that were apparently drawn in the grass of the National Mall in Washington DC. "Eighty-six" is a slang term for "get rid of", and Trump administration officials claim that the numbers are meant to encourage violence against Trump, the 47th president. US Park Police "responded to a report of vandalism" at around 11:30ET (16:30GMT) on Thursday morning, the agency said in a statement. "The cause of the discoloration has not yet been determined. Grass samples have been collected for testing. The investigation is ongoing." Images of the grass show the numbers 8, 6 and 7, but the number 4 is not clearly visible. The investigation comes as US prosecutors attempt to jail the former director of the FBI for a social media post in which the numbers were seen written on a beach in sea shells. James Comey is facing multiple charges related to an alleged threat to kill Trump. He has denied the charges and called the prosecution politically-motivated. The numbers have been used by opponents of Trump, and have appeared at protests against his administration. The slogan written in the grass appears somewhat faded, with the number 8