More than 400 items found in novichok investigation
More than 400 exhibits, samples and items have been recovered by police investigating the Amesbury novichok poisoning.
Searches are expected to continue for several weeks, if not months, as officers look for other possible sites or sources of contamination, as well as gather further evidence.
Dawn Sturgess, 44, died a week ago after she apparently handled a bottle contaminated with the nerve agent in Amesbury, Wiltshire.
Her partner Charlie Rowley, 45, remains in hospital where he is in a serious but stable condition.
Their exposure comes after ex-Russian spy Sergei Skripal and his daughter Yulia were poisoned with the same substance in Salisbury in March.
They recovered after many weeks in hospital.
Assistant Commissioner Neil Basu, head of counter terrorism policing in the UK,said: "It is not an exaggeration to say that the search process linked with both this and the Salisbury investigation has been one of the most complex and difficult that UK policing has ever faced.
"Not only are we trying to solve an extremely serious crime that has been committed, but we're also working to identify any potential outstanding risks to the public; all whilst ensuring that all those involved in the search process are not themselves exposed to any risk of contamination.
"It is painstaking and vital work, which unfortunately takes a very long time to complete, but I am sure that the public understands why it is absolutely necessary."
Meanwhile, Ms Sturgess's friends are planning their own memorial for her on Friday afternoon which is "open to anyone and everyone".
Ryan Knight, who knew Ms Sturgess through their time at the Salisbury homeless shelter John Baker House, said: "A lot of us probably won't be allowed to go to the funeral.
"I don't want to disgrace her funeral.
"I prefer not to turn up rather than get dirty looks.
"I'll be in the background.
"When her immediate family go, I'll go over and pay my respects."
Mr Knight described Ms Sturgess, who had three children, as having had " lots of friends", adding that the manner of her death was "something which is never expected".
"These are two innocent people."
Meanwhile, scientists at the Defence, Science and Technology Laboratory at Porton Down are carrying out further tests to confirm whether Ms Sturgess and her partner were affected by the same batch that poisoned the Skripals.
More from Amesbury poisoning
It is not yet clear where the contaminated bottle came from and how it came to be in Mr Rowley's home, where it was found.
Ms Sturgess's post mortem examination is scheduled to take place on Tuesday and an inquest into her death is set to open in Salisbury on Thursday.