The Parliament Square and Whitehall — the streets at the heart of British government were shut down by London police Monday evening due to an ‘incident’ surrounding a suspicious package.

Police shut down Whitehall — the historic avenue along which Britain’s government ministries and top military buildings are located — and the square outside the nation’s houses of Parliament after what was described as a “suspicious package” triggered an alert.

Exits leading onto Whitehall from the busy Westminster London Underground station were also closed.

Update 1915 — Whitehall reopened by Police

Monday evening’s incident concluded quickly, with police reopening roads in the area. No further details have yet been given by officers.

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Parliament Square, Whitehall, and the adjacent Trafalgar Square are set to host the annual million mask march Monday evening, a gathering of self-professed anarchists who wear masks from the Hollywood film V For Vendetta. Police said the incident was not related to the march.

There is currently a road closure on Whitehall between Parliament and Trafalgar Square in #Westminster due to a Police incident. This is not related to tonight's #MMM2018 event and the road will reopen as soon as possible. — MPS Events (@MetPoliceEvents) November 5, 2018

The alert comes 413 years to the day after an attempt to blow up Britain’s Houses of Parliament in the so-called gunpowder plot by dissident Catholics. November 5th is still celebrated in England with the lighting of bonfires and fireworks to remember the foiled plot.

This story is developing