A 45-year-old man named Charlie Rowley was still in hospital and is in critical condition.
The possibility that the two investigations might be linked is "clearly a key line of inquiry for police", the Met said. Although the United Kingdom has not officially blamed Russia for the latest poisoning, Russian officials have already denied any Kremlin involvement.
British Prime Minister Theresa May said she was "appalled and shocked" by the death of Sturgess, who had been living in a homeless hostel in Salisbury in southwest England. This has now become a murder investigation and police and security officials are working around the clock to establish the full facts of the incident.
Assistant Commissioner Neil Basu, the head of UK Counter Terrorism policing said: "This is shocking and tragic news".
Counter-terrorism police are also studying roughly 1,300 hours of CCTV in the hope of finding clues about the couple's activities in the hours before they became violently ill.
It was unclear if Williamson was referring to the attack on the Skripals or a new attack. That was because a Russian-developed nerve agent had been used against a man considered to be a traitor by Russian intelligence.
Sturgess died at Salisbury District Hospital, the same facility that nursed the critically ill Skripals.
Britain has blamed Putin's government for the poisoning of the Skripals, which triggered a diplomatic row in which Britain and its allies expelled more than 150 Russian diplomats.
A woman who was exposed to a military-grade nerve agent in the United Kingdom last month has died, authorities said Sunday.
Moscow says London has declined its offers for a joint investigation into the poisonings.
The language has pointed that way - for instance, the home secretary accusing Russian Federation of using the United Kingdom as a "dumping ground".
On Wednesday, the government's Defence Science and Technology Laboratory at Porton Down confirmed their exposure to Novichok.
Wiltshire Council announced that, just as it is in Salisbury, parking in the town centre auto parks will be free from 12.00pm midday Monday to Friday and free all day at weekends and Bank Holidays.
The BBC has reported that the risk of Novichok contact to the general public remains low.
Rowley regularly scavenged for goods to fix and sell, leading to the possibility that he and Sturgess might have inadvertently found the container used to transport the Novichok.
Ms Sturgess, 44, from Durrington, was rushed to hospital on Saturday 30 June after becoming ill at a house in Muggleton Road in Amesbury.
"We believe that in any case, it would be rather absurd", Peskov said.
Whilst 21 other people have come forward with health concerns, they have been screened and "all been given the all-clear", he said.