Investigators from the Organisation for the Prohibition of Chemical Weapons (OPCW) arrived in Damascus on April 14, reports CNN.
When the team visits the site on Wednesday, they are expected to gather soil and other samples to help identify the substances, if any, used in the attack that killed over 70 people.
Lavrov slammed the US, UK and France for carrying out the strikes on targeted Syrian properties on the night of April 13 which came as a retaliation to the Douma attack, before the OPCW team could conduct its investigation.
The missiles targeted Shayrat air base, but did not say who fired the missiles.
Another report, from the pro-Iranian Hezbollah militia, said that Syrian air defences had intercepted three missiles targeting Dumair military airport, north-east of the capital Damascus.
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