Earlier on Monday, Britain's top counter-terrorism officer said detectives were unable to say if the Novichok that poisoned Sturgess and a man who is in critical condition in hospital was from the same batch that struck down the Skripals.
The death of a British citizen, caused by a Soviet-era nerve agent that could have been brought to English soil by Russians, comes at a particularly sensitive time.
It may well be that it was Ms Sturgess who came into first contact and Mr Rowley received secondary contamination from her, but that remains to be confirmed.
Theresa May said she was "appalled and shocked" by her death. Moscow has rejected the accusations and has hit back by expelling Western diplomats.
Basu says more than 100 police are working to try and search all areas where Sturgess and Rowley had been before they became ill nine says ago. That afternoon, Rowley fell ill at the same address in Amesbury and was also hospitalised. Britain has blamed Russian Federation for the poisoning of the Skripals, but Russian Federation has denied involvement.
Police believe Sturgess, 44, and Rowley, 45, "must have handled a container" with the nerve agent inside it and were exposed to a "high dose" of the military-grade poison.
"This activity has centred on Dawn's address at John Baker House, Salisbury, Charlie's address in Muggleton Road, Amesbury, and Queen Elizabeth Gardens in Salisbury", Mr Basu said.
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The two Britons were initially thought to have taken an overdose of heroin or crack cocaine. Both towns are in the southeast of Wiltshire, not far from the UK's highly secretive Porton Down military science and technology laboratory.
Peskov went on to comment on a separate statement by Russia's representative at the Organization for the Prohibition of Chemical Weapons (OPCW), Alexander Vasilievich Shulgin.
Kremlin spokesman Dmitry Peskov said Russian Federation was "deeply concerned" about the incident in Amesbury - but said accusations that it was involved are "absurd".
Another Novichok nerve agent has struck the United Kingdom recently, claiming one life and leaving another in critical condition in the hospital.
Yulia Skripal, Sergei's daughter, was in a coma for 20 days after she was attacked and was eventually discharged about five weeks after the poisoning. Her father Stephen, 65, said his family was "devastated". The hospital's medical director, Dr. Christine Blanshard, said the staff "worked tirelessly to save Dawn". Neighbours said they did not know who the van belonged to.
Alastair Hay, a professor of environmental toxicology at Leeds University, said the hospital probably now had more experience than anywhere else in the world with Novichok cases, but there were limits to what doctors could do.
Britain has called on Russian Federation to answer questions about where the nerve agent came from.
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. Their investigation must be led by the evidence available and the facts alone.
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