Britain's top counter-terrorism officer says detectives are unable to say if the Novichok that two Britons were exposed to was the same that struck down a former Russian double agent and his daughter.
Dawn Sturgess, 44, died after she was exposed to Novichok on June 30, just a few miles from where Russian double agent Sergei Skripal and his daughter Yulia were attacked with the same poison four months ago.
"This latest horrendous turn of events has only served to strengthen the resolve of our investigation team as we work to identify those responsible for this outrageous, reckless and barbaric act," Neil Basu, Britain's most senior counter-terrorism officer, said.
"They are unable to say at this moment whether or not the nerve agent found in this incident is linked to the attack on Sergei and Yulia Skripal," Basu said.
Meanwhile, the Kremlin says it is sorry to hear of Sturgess' death, but says any suggestion that Russia is involved would be "quite absurd."
Russia has denied any involvement in the Skripal case and suggested the British security services carried out the attack to stoke anti-Moscow hysteria.
Peskov said the investigation and what was happening in the Salisbury area was a British domestic issue.
Police are investigating Sturgess' death as a murder, while British Prime Minister Theresa May says she's appalled and shocked by the death.
Police are investigating how Sturgess and a 45-year-old man, named by media as Charlie Rowley, came across an item contaminated with Novichok, which was developed by the Soviet military during the Cold War.
It was initially thought they had overdosed on heroin or crack cocaine but tests at the Porton Down military research centre showed they had been exposed to Novichok after touching a contaminated item with their hands, police said on Sunday.