New Delhi, June 12 -- A large "8647" message appearing across a section of Washington's iconic National Mall has triggered an investigation by US authorities, days before thousands of people are expected to gather in the area for a major event linked to US President Donald Trump.

The numbers were spotted etched into the grass east of the World War II Memorial and were clearly visible from aerial views and live webcams positioned atop the Washington Monument, CNN reported.

Images showed the numbers formed by patches of dead or discoloured grass spread across a large portion of the National Mall. It remains unclear exactly when the markings first appeared.

According to CNN, photographs taken on June 5 did not show any sign of the message...