Chemical inspectors from the Organization for the Prohibition of Chemical Weapons completed on Friday their mission to the Syrian town of Douma, the site of last month’s chemical attack by the regime.
The global watchdog said: “The initial deployment of the fact-finding mission... in Douma is complete.”
"Samples have been brought to the OPCW laboratory where they will be split and then dispatched to the OPCW designated laboratories," it added in a statement.
The OPCW's mission to Douma was launched amid international outrage over images of adults and children suffering from the effects of a toxic weapon attack.
The gruesome footage from the apparent April 7 attack horrified the world and prompted unprecedented Western strikes on Syrian regime installations.
The fact-finding mission gained access to Douma on April 21 after several delays since deploying to Syria on April 14.
But the global watchdog warned that the analysis of samples "may take at least three to four weeks," with inspectors continuing to collect more information and material.
"At this time it is not possible to give a timeframe for when the Douma report will be issued to states parties to the Chemical Weapons Convention," the OPCW said.
On April 7, the Syrian American Medical Society (SAMS) and the White Helmets jointly said dozens of people died in a "poisonous chlorine gas attack" in Douma.
Later on Friday, diplomatic sources told Reuters that Western powers were weighing a French proposal to create a new mechanism at the OPCW that would enable it to assign blame for attacks with banned munitions.
The OPCW in The Hague currently only determines whether such attacks have taken place, not who carried them out.
A new mechanism could fulfil that role, which had been carried out since 2015 by a joint United Nations-OPCW investigation in Syria until its renewal was vetoed by Russia in November.
"On Syria everything is blocked at the UN Security Council and in general we are seeing repeated and systematic flouting of multilateral frameworks, including proliferation of chemical weapons," said a senior French diplomat.
"We need a mechanism to apportion blame. Salisbury was a step too far."
Creating a global mechanism for accountability is also seen as important due to a rising number of incidents with nerve agent since they were banned two decades ago under an international treaty.
Recent use includes the assassination with VX of Kim Jong Nam, half-brother of North Korean leader Kim Jong Un, in Kuala Lumpur airport in February 2017 and the attempted murder of Sergei Skripal, a 66-year-old former Russian double agent, and his 33-year-old daughter Yulia, with a Novichok nerve agent in March in Salisbury, England. They both survived.
But the French proposal is also likely to meet resistance from Russia, Iran and others. Decisions at the OPCW are usually put to a vote by the 41-seat executive council, where 27 votes are needed to pass. Recent initiatives at the OPCW to condemn Syria for using chemical weapons have not garnered enough support.
The alternative is to go to the OPCW's full 192-seat conference of states, which can intervene to ensure compliance with the 1997 Chemical Weapons Convention, which has been violated repeatedly by the use of sarin, chlorine and Sulphur mustard gas in Syria, as well as the attacks in England and Malaysia.
French President Emmanuel Macron discussed the new OPCW mechanism with the head of the OPCW, Ahmet Uzumcu, during a visit to the Netherlands in March. France is working with its close allies on the details of how the system would work, another source said.
