Sergei Skripal and his daughter Yulia remain in a critical condition
Hundreds of people have been told to wash their possessions following the discovery of traces of a nerve agent in Salisbury, England.
However, health officials there insist the risk to the public is still "very low".
Public Health England (PHE) issued "precautionary advice" a week after former Russian spy Sergei Skripal and his daughter Yulia were found slumped on a bench in the city.
This was in response to traces of a nerve agent being discovered at The Mill pub and the nearby Zizzi restaurant.
It said those who visited the pub between 1.30pm last Sunday and 11.10pm on Monday, and the restaurant between 1.30pm on Sunday and 9pm the next day, should take action.
Those who visited either of the two locations within the specified time frame should:
The health risk to residents in Salisbury remains low. We have issued a statement on the precautionary advice for those who were in The Mill pub or Zizzi restaurant in Salisbury on Sunday 4 or Monday 5 March 2018 https://t.co/Tr6KOXMnjV— PublicHealthEngland (@PHE_uk) March 11, 2018
Dr Jenny Harries, joint director at PHE England, defended the decision to issue the guidance a week after the poisoning.
She said: "It's really important to understand the general public should not be concerned. There is, on the evidence currently, a very low risk.
"We work with our colleagues here on a continuous risk assessment basis. When we get new information we continuously risk-assess groups of people who may have become exposed, from the evidence we have in front of us.
"As new evidence becomes available, we act on that immediately. Most people who will have been at the pub will have washed the clothes they were in.
"The immediate risk - we're not anticipating, on our current evidence, seeing new patients coming forward.
"This is about a very, very small risk of repetitive contact with traces of contamination that people may have taken out.
"The advice we're giving today about washing clothes - very simple things... that will remove that risk as we go forward."
Fewer than 500 people would have been in either venue, according to chief medical officer Professor Sally Davies.
She said: "Rigorous scientific analysis continues, but we have now learnt that there has been some trace contamination by the nerve agent in both The Mill pub and Zizzi's restaurant in Salisbury.
"I am confident this has not harmed the health of anyone who was in The Mill pub or Zizzi's restaurant.
"However, some people are concerned that prolonged long-term exposure to these substances may, over weeks and particularly months, give rise to health problems.
"I'm therefore advising - as a belt and braces approach - that people who were in [Zizzi's or the Mill during the specified times]... should clean the clothes they wore and the possessions they handled while there.
"This is precautionary advice aimed at only those people who were at the venues at these times, which I believe to be below 500 people."
Mr Skripal and his daughter remain in a critical but stable condition in hospital.
Police Detective Sergeant Nick Bailey - who was taken to hospital after falling seriously ill when he responded to the emergency - is conscious and in a serious but stable condition.
The pub and restaurant are among a number of locations that have been cordoned off across the city.