Britain's home secretary is visiting Amesbury and Salisbury in southwestern England to reassure residents that the risk to the public remains very low despite the recent poisoning of two people exposed to a deadly nerve agent.
Sajid Javid said Sunday that both towns remain open for business and urged people to visit.
More than 100 police officers are working to try to locate a small vial believed to have contained the nerve agent Novichok, which was manufactured in the Soviet Union during the Cold War.
The nerve agent was used in the March attack on an ex-Russian spy Sergei Skripal and his daughter Yulia, and two Britons have been critically ill since they were exposed to it eight days ago.
Police think 44-year-old Dawn Sturgess and her partner, 45-year-old Charley Rowley, had secondary exposure to the chemical weapon used in the attack on the Skripals.
Several sites remained cordoned off as a laborious search continues.
A police officer also underwent a precautionary test at a hospital to check for possible contamination related to the case, but Wiltshire Police said on Saturday that he had been cleared.