The cause of the emergency reportedly remains unknown.
The terror threat remains high in the United Kingdom. The country has faced a number of deadly terror acts in recent years, most notably the attack on London's Westminster Bridge and parliament grounds in March 2017, as well as a concert bombing in Manchester on 22 May 2017.
In January, Scotland Yard said that around 200 UK jihadists who had travelled to Syria to fight alongside the Daesh terrorist group are thought to be alive and might decide to come home, something that would be a serious threat to national security.
* Daesh (also known as ISIS/ISIL/Islamic State/IS) is a terrorist group banned in Russia.