Inspectors from the Organization for the Prohibition of Chemical Weapons entered the Syrian town of Douma on Saturday to look into allegations of chemical weapons use.
The site visit would allow the agency to proceed with an independent investigation to determine what chemicals, if any, were used in the alleged attack on April 7.
The OPCW will evaluate the situation and consider steps including another possible visit to Douma, according to a statement.
It added that the collected samples will be transported to the OPCW laboratories in Rijswijk in the Netherlands for analysis.
The visit comes as a United Nations security team entered Douma on Friday to assess the security situation before the visit of the OPCW experts after a previous attempt ended when the team came under small-arms fire on Tuesday.
The arrival of the OPCW inspectors came after the Syrian government invited the OPCW to investigate the April 7 incident, when rebels and activists accused the Syrian forces of using chlorine gas in an attack on Douma, just outside the capital Damascus.
The Syrian government denied the allegations, saying the rebels and their foreign backers were fabricating events to attract foreign military action.
On April 14, the United States, France and Britain launched a series of missile strikes on Syrian positions over the allegations, with the OPCW team arriving on the same day.
On Saturday, Syria's Assistant Foreign Minister Ayman Sussan said that investigating the chemical weapons allegations in Douma will expose the "lies" of the Western countries.
Sussan said it was the Syrian government who invited the OPCW to look into the allegations about the use of chlorine gas ahead of the withdrawal of the rebels and their families to northern Syria.
"The Syrian government has declared in its invitation letter (to the OPCW), and after the arrival of the (inspection) team, it will fully cooperate and offer all facilitations for the inspection team to carry out its mission," he said.
He added that this "will be of a great interest for us because when the investigation team conducts its work it will expose the lies of the Western allegations and the accusations they have made about the alleged attack in Douma".
Sussan slammed the US and its Western allies for overstepping their boundaries in launching the missile attacks.
"If they are saying that chemical weapons were used in Ghouta, and if the US or France and Britain really wanted to know the truth, they should have provided appropriate conditions for the OPCW to carry out its mission," he said.
On Saturday, rebels began evacuating three towns in the eastern Qalamoun region in the Damascus countryside, state television reported.
Al-Ikhbariya TV said 35 buses left the towns of Ruhaiba, Jayroud and al-Nasriya carrying hundreds of rebels and their families to opposition territory in northern Syria.
The station said there could be 3,200 rebels leaving three towns on Saturday. It said the evacuations would continue for three days.
Syrian government forces will take over the towns once the departures are complete.
سایت تابناک از انتشار نظرات حاوی توهین و افترا و نوشته شده با حروف لاتین (فینگیلیش) معذور است.