"There's been around 21 people (treated)", said Kier Pritchard, chief constable for Wiltshire Police, noting that included "multiple officers".
"Of course he's very anxious, he's very concerned".
Both victims remain unconscious, in a critical but stable condition, while a British police officer who was also harmed by the substance is now able to talk to people although he remains in a serious condition, interior minister Amber Rudd said.
Ms Rudd said the poisoning "was attempted murder in the most cruel and public way".
The British government deployed the military Friday to help with its probe of the mysterious nerve-agent poisoning of a former Russian spy and his daughter - an apparent assassination attempt that also left 19 others seeking medical treatment.
Russian exile Valery Morozov told Sky News Mr Skripal had been in contact with the Russia and visited its London embassy once a month.
"But the best way to get to them is to give the police the space they need to really go through the area carefully, to do their investigation and to make sure that they have all the support that they need".
Police say they know the nerve agent used in the attack but have declined to say what it was or how they suspect it was administered.
"In terms of further options, that will have to wait until we're absolutely clear what the consequences could be and what the actual source of this nerve agent has been", Ms Rudd said.
Specialist investigators wearing protective suits have been seen examining the bench that the pair collapsed on.
Police have cordoned off sites including ex-spy Sergei Skripal's house, a vehicle, the cemetery where his wife is buried, a restaurant and a pub.
Those branded enemies of the Russian state have sometimes died mysteriously overseas, and the Skripal case echoes the death of Alexander Litvinenko, a former Russian agent who was poisoned in London in 2006 with radioactive polonium-210.
Russian Federation has denied responsibility for the attack, which comes seven years after Mr Skripal was released from the country as part of a spy swap with the US.
The Organisation for the Prohibition of Chemical Weapons, the global chemical weapons watchdog based in The Hague, said on Thursday (local time) the Skripal case was "of great concern", adding that it was in touch with British authorities over the attack.
They were exposed by a former Russian intelligence officer who had been leaking classified information to the U.S. since at least 1999.
Kremlin foreign ministry spokeswoman Maria Zakharova told reporters the story "was straight away used to boost an anti-Russian campaign in the media".
It cited Boris Berezovsky, a friend of Litvinenko found hanging in his bathroom in 2013, and Alexander Perepilichny, a businessman found dead in front of his home.
The cause of 59-year-old Ms Skripal's death was recorded as endometrial cancer and Alexander, 44, was said to have suffered liver failure while on holiday.
The Russian government has denied any involvement in the Litvinenko killing or the attempted killing of Skripal, a former Russian agent who had served jail time in his homeland for spying for Britain before being freed in a spy swap.
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