(CNN) - British police have identified two suspects in the poisoning of former Russian double agent Sergei Skripal and his daughter, Yulia, a source said.
Police believe the two suspects left the United Kingdom for Russia after the poisoning, a source with knowledge of the investigation told CNN.
The Skripals were exposed to Novichok back in March.
Novichok is a Soviet-era nerve agent.
A source tells CNN the two suspects in the poisoning were identified using CCTV footage and facial recognition technology.
They're not known to be spies or to have been used in other attacks before.
Last month, in a neighboring town, two more people were poisoned.
The woman, Dawn Sturgess died. Her partner Charlie Rowley remains in hospital.
Novichok was also the culprit in that case.
However, investigators have not been able to confirm that it was from the same batch used to poison the Skripals.
Investigators have cross-checked that information with the manifest of the commercial flight the suspects were believed to have left Britain on soon after the attack. Those names were aliases, the source said, and police have not yet revealed them.
UK police tell CNN they are not commenting.
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