Image copyright EPA/ Yulia Skripal/ Facebook Image caption Sergei Skripal, 66, and his daughter Yulia, 33 were poisoned by a nerve agent called Novichok A Russian ex-spy and his daughter first came into contact with the nerve agent that poisoned them at their home, police have said.
The highest concentration of the agent use against Sergei and Yulia Skripal was found on their front door.
The pair were found collapsed on a bench in Salisbury on 4 March and remain in a critical condition.
Police said inquiries would focus on their home address in Christie Miller Road but the risk to locals was low.
Traces of the nerve agent had been found at some of the other sites in the city, but they were at lower concentrations.
Russian spy: What we are all familiar with so far Nato slashes Russia staff after poisoning Skripal niece: ‘I'd really like to know how they are' Image caption Specialist officers in protective suits procured the scene following the nerve gas assault Image caption Police are appealing for witness who assured Mr Skripal's car on the morning of the incident Media captionEurovision-style? The BBC's Steve Rosenberg on how the Russian media is reporting the score-settling Image caption Col Skripal, 66, had been living in Salisbury after being released by Russia in 2010
