The suspected perpetrators responsible for the novichok attack on former Russian spy Sergei Skripal and his daughter have been identified by the police, according to latest reports.

“Investigators believe they have identified the suspected perpetrators of the novichok attack through CCTV and have cross-checked this with records of people who entered the country around that time. They (the investigators) are sure they (the suspects) are Russian,” a source with knowledge of the investigation told British-based news agency Press Association.

Ever since the Skripals were attacked, the Metropolitan police have been scanning through thousands of hours of CCTV footage attempting to spot the attackers. According to the Guardian, it is possible that the police finally found the needle in a haystack or got a fresh lead on the location of the bottle which made them focus on the footages of some specific areas of the country, narrowing down the list of suspects.

The police believe more than one Russian was involved in the attempted assassination of Skripal, who worked as a former double agent for MI6 spy service, and his daughter, Yulia, in Salisbury, England, in March.

The recent development came after the same batch of nerve agent that poisoned the Skripals, also claimed the life of another victim — Dawn Sturgess, 44 — earlier this month and left her partner Charlie Rowley, 45, critically ill. It is believed that the woman came into contact with 10 times the amount of novichok the Skripals were exposed to.

Sturgess died eight days after coming in contact with the deadly nerve agent, believed to be in a perfume bottle found in a park or elsewhere in Salisbury city center. Rowley said he picked up the bottle — which was discovered in his home by investigators — and gave it to his partner, who sprayed it directly on her skin.

As to where Rowley found the bottle is still being determined. The police carried out a fingertip search of Salisbury’s Queen Elizabeth Gardens, where Sturgess and Rowley had spent time before falling ill. In addition to the park, other areas of Salisbury and nearby Amesbury were sealed by the police last month after the duo fell seriously ill.

As many as 400 potentially contaminated items were removed from the public places and sent to the government’s Porton Down defense laboratory for testing. Furthermore, samples collected by the Organisation for the Prohibition of Chemical Weapons (OPCW) — called in to carry independent checks on the substance that poisoned Sturgess and Rowley — were sent to two separate labs and the reports were relayed back to the U.K.

After the recent attack, Public Health England warned the public that although the risk of coming in contact with the lethal substance that killed the Skripals and Sturgess was low, it was best to stay away from discarded items like syringes, needles, cosmetics or similar objects made of materials such as metal, plastic or glass.

The inquest for Sturgess’ death is scheduled for Thursday in Salisbury and is expected to be adjourned to allow police inquiries to continue. The opening statement at the inquest will be given by the coroner for Wiltshire and Swindon.

Military personnel wearing protective suits remove a police car and other vehicles from a public car park as they continue investigations into the poisoning of Sergei Skripal in Salisbury, England, March 11, 2018. Getty Images/ Chris J Ratcliffe