Whitehall was completely cordoned off after a suspect package sparked a police incident on Christmas Eve, eyewitnesses have claimed.
A video from the scene showed police tape stretching across the road with a number of officers standing guard.
At least three police cars were stationed at the scene, with blue lights flashing.
Unconfirmed reports suggested that a suspicious package was reported in the area, with one claim of a laptop shutting Horse Guards Parade.
Whitehall 'completely cordoned off' after 'suspect package' sparks police incident
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The Metropolitan Police has since confirmed that the incident is now over.
Officers had been called to respond to an item found near Horse Guards Parade.
Following an inspection, Scotland Yard stood down the incident.
However, eyewitness accounts suggested Whitehall had been closed between Parliament Square and Trafalgar Square at lunchtime.
One person said: "Anyone know why Whitehall is completely cordoned off?"
Another commented: "Whitehall has been closed off and Horse Guards evacuated because of a suspect package."
A third person wrote: "Suspicious item. Things have now been stood down."
Horse Guards is the official entrance to St James's and Buckingham Palace.
It dates from the 18th century and was designed by King George II's chief architect William Kent.
Horse Guards remains an iconic attraction for tourists, with many gathering to snap a photo alongside a member of the King's Guards.