A total of 21 people have been treated as a result of the nerve agent attack in Salisbury.
Three people now remain in hospital: Russian ex-spy Sergei Skripal, his daughter Yulia and the officer who was one of the first to arrive at the park bench where the pair were found.
He has been named as police sergeant Nick Bailey, who is described by colleagues as "well-liked, well-loved and a massively dedicated officer".
The 38-year-old, who has been with the force since 2002, remains in a serious condition, but is now "talking and engaging" with people.
Acting chief constable of Wiltshire Police, Kier Pritchard, visited Mr Bailey in intensive care, describing him as "very anxious and very concerned. He did his best on that night".
Sergei Skripal and Yulia are described as being in "a very serious condition".
:: What is a nerve agent and how does it work?
New photos and a video of 33-year-old Yulia have now emerged, showing her enjoying a holiday in Munich and out and about in the capital.
Mr Skripal's Wiltshire home is now one of the major crime scenes, and forensic officers have begun a fresh fingertip search of the house.
The multiple people treated following the poisoning include members of the public, police and the emergency services.
Mr Pritchard said: "A number of those have been through the hospital treatment process, they are having blood-tests, support and advice."
Prime Minister Theresa May said her thoughts were with all the victims, praising the response of the emergency services.
She said the incident was "a stark reminder, if ever one was needed, of the dangerous situations our emergency services face and the dedication and courage they display every day in order to keep us safe".
:: Russia row: How will UK respond to spy 'attack'?
Home Secretary Amber Rudd has threatened a "robust" response to the "brazen and reckless act" committed on UK soil.
Ms Rudd asked "who is responsible for this most outrageous crime?" and said the poisoning "was attempted murder in the most cruel and public way".
While she said speculation must be avoided, she said "people are right to want to know who to hold to account".
She said the Government were "committed to doing all we can to bring the perpetrators to justice – whoever they are and wherever they may be".
More from Salisbury spy
The Kremlin has insisted it is not involved, and said any allegations are a plot to whip up anti-Russian sentiment.
President Putin has yet to respond to the news that nerve agent was involved in the poisoning.
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