Police officers responded to a “suspicious” envelope containing white powder delivered to Britain’s Houses of Parliament in Westminster, London Tuesday afternoon.

A spokesman for the Commons said of the investigation: “The Police are currently investigating an incident on the Parliamentary Estate.”

While the investigation was originally reported to involve a “suspicious package”, a police statement later clarified that it was an envelope containing white powder.

London’s Metropolitan Police said: “At approximately 1136hrs on Tuesday, 13 February, police were informed of a suspicious package that had been delivered to an office within the Palace of Westminster.

“The letter contained a white powder which is currently being assessed by specialists. The office remains closed at this time, but the rest of the Palace of Westminster is open.

“Detectives from the Met’s Counter Terrorism Command have been informed and are investigating.”

Security surrounding Britain’s Parliament remains high after a number of terror attacks in the country in the past 12 months, including one against Parliament itself, when Islamic radical killer Khalid Masood drove a car into pedestrians, before proceeding on foot and stabbing a police officer in the Palace Yard to death.

This story is developing…