Sept. 5 (UPI) — Six months after a former Russian double agent and his daughter were poisoned in Britain, authorities have identified and charged two people in the high-profile case.

British prosecutors announced the new development Wednesday. The suspects — Alexander Petrov and Ruslan Boshirov — were charged with the March 4 poisoning of Sergei and Yulia Skripal in Salisbury, Britain.

Prosecutors said the pair are in Russia and cannot be extradited.

“We have, however, obtained a European arrest warrant, which means that if either man travels to a country where [the arrant] is valid, they will be arrested,” said Sue Hemming, legal director of Britain’s Crown Prosecution Service.

Prosecutors said they used surveillance video and passport records to tie Petrov and Boshirov to the attack. Officials said they traveled from Moscow to London using Russian passports two days before the poisonings.

The men will also be charged with possession of novichok, a deadly Soviet-era poison that’s banned by the Chemical Weapons Act. Police say the nerve agent was smuggled into the country in a perfume bottle.

Prosecutors believe the men sprayed novichok on the front door of the Skripals’ home in Salisbury. Both Sergei and Yulia Skripal became seriously ill, but ultimately recovered.

Months later, two Britons, Dawn Sturgess and Charlie Rowley, were poisoned by the same nerve agent. Sturgess later died, but no one has been charged in that case. Authorities believe the pair somehow came into contact with the same novichok that sickened the Skripals.

Britain, the United States and other Western nations have accused the Russian government of having the Skripals poisoned. The Kremlin, though, has denied involvement.

Russian President Vladimir Putin has called Sergei Skripal, who spied for Russia and then Britain, a traitor for selling state secrets.