Inspectors from the Organization for the Prohibition of Chemical Weapons (OPCW) are arriving in the U.K. to assess samples of the nerve agent used in the attack against former Russian double-agent Sergei Skripal and his daughter earlier this month.
The OPCW team will study the substance at the military research facility Porton Down, which is located just outside the city of Salisbury, where the attack took place.
The team will also meet with detectives leading the investigation into the poisoning attack.
The British government invited the delegation from the Hague, where the monitoring body is based, to carry out an independent study to identify the substance used in the attack.
U.K. officials believe the Skripals were exposed to a military-grade, Soviet-era nerve agent developed by the Russians.
On Sunday ABC News revealed that intelligence officials believe the substance is a “dusty” organophosphate akin to the Novichok chemicals, and may have been administered through the car’s ventilation system.
The intelligence officials told ABC News up to 38 individuals in Salisbury were affected by the nerve agent but the full impact is still being assessed and more victims sickened by the agent are expected to be identified.
It will be weeks before the OPCW announces the results of its tests.