The nominally retired double agent Sergei Skripal spent several weeks in a coma after being discovered on a bench in Salisbury in March; he eventually recovered enough to be released from the hospital.
A preliminary investigation revealed Sturgess and Rowley were allegedly exposed to the military-grade nerve agent through a contaminated item that was linked to a March attack that poisoned ex-Russian spy Sergei Skripal and his daughter, Yulia, in Salisbury.
Police said there is no evidence that either Sturgess or Rowley visited any of the sites where the Skripals may have been poisoned.
Assistant Commissioner Neil Basu, the head of UK Counter-Terrorism policing, said: "This bad news has only served to strengthen our resolve to identify and bring to justice the person or persons responsible for what I can only describe as an outrageous, reckless and barbaric act".
On June 30, 44-year-old Dawn Sturgess and 45-year-old Charles Rowley were hospitalized in critical condition in the British town of Amesbury.
Russian Federation hit back, denouncing Britain for playing "dirty political games".
The Kremlin has slammed allegations of Russian links to the death of a woman who was exposed to Novichok as "absurd".
The Skripals fell ill after the poison was applied to the ex-spy's front door in the city of Salisbury.
The road is close to where Sturgess's parents live and two miles from Amesbury.
Specialists at the nearby Defense Science and Technology Laboratory at Porton Down, a military research facility, identified the agent used against the Skripals, Sturgess and Rowley as Novichok.
Police are continuing to hunt for a contaminated container which they believe was handled by the pair.
The poisoning of the Skripals was the first known offensive use of such a chemical weapon in Europe since World War Two.
The poisoning of Sergei Skripal and his daughter triggered an global outcry against Russian Federation, despite the Kremlin's denials that it was involved in the attack against the ex-double agent, while offering conflicting explanations about how they fell ill in Salisbury. A 45-year-old man also remains critically ill in hospital.
"The circumstances in the Amesbury situation are troubling: recently, such cases emerge ahead of important events", Aleksandr Shulgin, Russia's envoy to the Organization for the Prohibition of Chemical Weapons, was quoted by the Izvestia newspaper as saying in an interview published July 9. Her father Stephen, 65, said his family was "devastated".
The hospital's medical director, Christine Blanshard, told the BBC that hospital staff worked tirelessly to save Sturgess.
Britain's public health authority acknowledged on Friday the concerns of people living in the area after the two incidents involving Novichok, but said it was confident that the risk to the public remained low.