A team of United Nations inspectors arrived in Damascus Sunday to investigate the possible use of chemical weapons in Syria's civil war.
The 20-member team did not speak to reporters as they arrived at a hotel in the Syrian capital to begin their two-week mission.
The group will try to establish only whether chemical weapons - including sarin and other toxic nerve agents - were used, not who used them.
Led by Swedish arms expert Ake Sellstrom, the team's efforts to visit Syria had been repeatedly delayed since early April while negotiations continued over the access Damascus would grant them.
The mission will be limited to investigating the alleged use of chemical weapons in three areas, including a March attack in the Aleppo suburb of Khan al-Assal, which President Bashar al-Assad's forces and rebels blame on each other.
Khan al-Assal is under rebel control and the opposition says investigators will have full access. The other two sites have not yet been specified.
Assad's government and the rebels fighting him have accused each other of using chemical weapons, a step which the United States had said would cross a "red line" in the conflict which has killed 100,000 people.