This comes after the convoy of UN inspectors, who were due to begin a second day of investigation into the alleged chemical use in the Arab country, came under attack a day earlier.
On Monday, snipers fired multiple shots at the team of inspectors as they tried to visit an area in west of Damascus, forcing them to suspend their mission.
Damascus blamed foreign-backed militants for the attack, saying they are trying to force UN experts to cancel their work.
UN spokesman Farhan Haq told reporters that the first day of investigation had been “very productive,” and that the team was “already gathering valuable evidence.”
UN Secretary General, Ban Ki-moon, also said despite the “very dangerous circumstances,” the experts have “interviewed witnesses, survivors and doctors” and “collected some samples”.
Hundreds of people were killed and scores of others injured in a chemical attack in the Damascus suburbs of Ain Tarma, Zamalka and Jobar on August 21.
Both the Syrian government and the foreign-backed opposition accuse each other of being behind the deadly attack.
The Damascus government, however, has vehemently denied the accusations, saying the chemical attack was carried out by the militants themselves as a false-flag operation.
In March, dozens of people were killed in a chemical attack in the northern province of Aleppo. A Russian-led inquiry said that militants were behind the deadly attack.
Syria has been gripped by deadly unrest since 2011. The United Nations says more than 100,000 people have been killed and millions displaced since the outbreak of the violence.