New sites are being looked at by police following the attempted poisoning of former Russian double agent Sergei Skripal and his daughter Yulia.
The Met Police said: There are a number of scenes in place in Wiltshire, linked to the investigation into two people being taken ill in Salisbury on Sunday, 4 March.
The Counter Terrorism Policing network is leading the investigation into the events in Salisbury because it has the specialist expertise to do so, the Met said.
Emergency services attended a business park in Amesbury, north of Salisbury, on Monday as the investigation continues.
Parts of Solstice Park, including an ambulance station, were cordoned off by firefighters.
The incident has not been declared a terrorist incident at this stage but officers are keeping an open mind as to what happened, Met Police added.
Assistant Commissioner Mark Rowley, head of counter terrorism policing, said that while events in Salisbury were being taken extremely seriously, officers did not think there was any current risk to the wider public.
A meeting of the Government’s emergency COBRA committee will take place on Wednesday to discuss the suspected poisoning.
Yvette Cooper, chair of the Home Affairs Select Committee, has written to Home Secretary Amber Rudd calling for an investigation into 14 deaths that have not been treated as suspicious by the UK police, but have – reportedly – been identified by United States intelligence sources as potentially connected to the Russian state.
Mr Skripal, 66, and his daughter Yulia, 33, are in a critical condition in intensive care at Salisbury District Hospital.
He was convicted in Russia of spying for MI6 in 2006, and later given refuge in the UK as part of a spy swap.
Yulia currently works for Pepsico in Moscow, according to her Facebook account, after moving to Britain for a few years in 2010.
Theresa May chaired a meeting of the National Security Council on Monday.
The PM and senior ministers were also updated following another meeting of senior government officials earlier in the day, Downing Street said.
A witness who saw them has spoken to Sky News.
She said: They were just slumped. They were comfortable, they weren’t in any pain or anything. Lifeless, if you like.
When you walked past, they didn’t even acknowledge that you’ve walked past. They just stayed slumped.
A branch of the Zizzi restaurant chain in Castle Street, Salisbury, has been closed as a precaution.
The Russian embassy, meanwhile, has accused the media of launching a new phase of the anti-Russian campaign ongoing in the UK.
Readers are offered various speculations which ultimately lead to a vilification of Russia, it claimed.
In a statement, the embassy added that the police and other British authorities had not provided it with any official information regarding this incident.
The Foreign Office has not given any notifications either, it said.
But Foreign Secretary Boris Johnson told MPs the case of Mr Skripal and his daughter had echoes of the death of Alexander Litvinenko.
Mr Litvinenko, a Russian dissident, was fatally poisoned in London in 2006.
Answering an urgent question in the Commons, Mr Johnson said that should evidence emerge that implies state responsibility, then Her Majesty’s Government will respond appropriately and robustly.
Russia was in many respects a malign and disruptive force, he added.
Responding to Mr Johnson’s comments, the Russian embassy said he had spoken in such a manner as if the investigation was already over and Russia was found responsible for what happened in Salisbury.
A former associate of Mr Litvinenko claimed the incident in Salisbury bore the hallmarks of a state-ordered assassination.
Historian Yuri Felshtinsky said that poisoning is the method of choice for the FSB (Russia’s Federal Security Service).