THE ongoing investigation into the poisoning of Sergei and Yulia Skripal returned to the centre of Salisbury today, when police raided John Baker House.

Police tape cordons at Elizabeth Gardens and the town path, Salisbury bus depot and a bin on the corner of Rollestone Street had been in place in Monday.

But today (Thursday) the police presence was increased, and Rollestone Street has now been completely closed to the public.

Businesses operating in the street can only access their buildings with a police escort.

Green protective barriers have been erected in the street around John Baker House, where one of the victims - Dawn Sturgess - is believed to have lived.

Ms Sturgess and her partner Charlie Rowley are the latest to fall ill after exposure to Novichok in the city, bringing the known total to five people in four months.

At a press conference this afternoon representatives from Wiltshire Police, Public Health England and Wiltshire Council failed to answer questions about how the pair came to be contaminated months on from extensive cleaning within the city.

It is believed that they came into contact with a container that held the original nerve agent used to poison Russian former-spy Sergei Skripal in March.

The public have again been advised to wash their clothes and wipe down items with baby wipes, but have also been told not to "pick up anything if you don't know what it is".

Deputy Director for Public Health England in the South-West Debbie Stark could not clarify what item this may be.