A total of 21 people were treated due to exposure to the nerve agent used to poison a Russian double agent.
The figure includes Russian ex-spy Sergei Skripal, his daughter Yulia and police officer Nick Bailey, who all remain seriously ill in hospital.
After the magnitude of the incident was realised by authorities, firefighters donned hazmat suits to secure the forensic tent over the bench where Mr Skripal and his daughter were found.
Earlier today Amber Rudd said that the nerve agent used in the Salisbury attack was ‘very rare’, though she declined to say whether she knows exactly what it was.
Addressing speculation on who was responsible for ‘this most outrageous crime’, the Home Secretary added: ‘The use of a nerve agent on UK soil is a brazen and reckless act. This was attempted murder in the most cruel and public way. People are right to want to know who to hold to account.
‘But if we are to be rigorous in this investigation, we must avoid speculation and allow the police to carry on their investigation.
‘We are committed to doing all we can to bring the perpetrators to justice, whoever they are and wherever they may be.
‘The investigation is moving at pace and this Government will act without hesitation as the facts become clearer.”
While Sir Edward Leigh, a Conservative former minister, said the circumstantial evidence against Russia was ‘very strong’, adding: ‘If Russia is behind this, this is brazen act of war, of humiliating our country.’
Downing Street said Theresa May was being kept updated by officials on developments in the Salisbury case.
The Prime Minister’s official spokesman said: ‘It’s clear that this was an appalling and reckless crime and the public will rightly want those responsible to be identified and held to account.
‘But it is important that we avoid speculation and allow police and others to rigorously establish the full facts.
‘As the Home Secretary and Foreign Secretary have made clear, our response to those found to be responsible will be robust.’
The spokesman said Mrs May sent her personal thanks to police and emergency workers for their courage in responding to the incident.
Wiltshire Police praised Detective Sergeant Bailey for his response to the incident.
Temporary chief constable of Wiltshire Police Kier Pritchard said: ‘I did go and see Nick today and I met Nick and his wife at the hospital in the intensive care unit.
‘I’ve known Nick for many years, he’s a great character, he’s a huge presence in Wiltshire Police – well liked, well loved, a massively dedicated officer. He’s clearly receiving high specialist treatment.
‘He’s well, he’s sat up. He is not the Nick that I know but of course he’s receiving a high level of treatment. He’s in the safe hands of the medical professionals working in Salisbury District so I’m very confident he’s getting the best professional support that he can.
‘Of course he’s very anxious, he’s very concerned. He did his very best on that night.
‘All of our staff that attended the incident in Salisbury in the Maltings, they performed the role that police officers and police staff do every day up and down the country. Limited information, responded to try and protect people and safeguard people who we knew were ill.
‘I’m massively proud of what Nick did and all of my staff on that night, they did a first-class job.’