A U.N. delegation tasked with investigating the reported use of chemical weapons in the Syrian conflict arrived in Damascus on Wednesday to discuss terms of a possible probe into alleged attacks.

This is the first such trip by international experts and the talks are expected to focus on about a dozen incidents in which chemical weapons were allegedly used. The rebels, the U.S. and others have blamed the regime for attacks, while Damascus and its ally Russia say the rebels have used chemicals.

Damascus has requested the U.N. to investigate one of the reported attacks — a March 19 incident in the northern village of Khan al-Assal in which both rebels and the government accuse each other of using chemicals — but refused inquiries at other alleged attack sites in the central city of Homs, Damascus and elsewhere.

Swedish chemical weapons expert Ake Sellstrom and U.N. disarmament chief Angela Kane arrived from neighboring Lebanon and are scheduled to meet with senior Syrian officials during their two-day visit to Damascus, the U.N. said in a brief statement issued in the Syrian capital.

Khan al-Assal, which lies on the southwestern edge of the embattled city of Aleppo, was under government control in March but was captured by the rebels earlier this week. Even if the U.N. team does get access to Khan al-Assal from both sides, it may be difficult to find evidence from the attack because so much time has passed.

In June, the United States said it had conclusive evidence that President Bashar Assad’s regime used chemical weapons against opposition forces. That crossed what President Barack Obama called a “red line,” prompting a U.S. decision to begin arming rebel groups, although that has not happened yet.

On Tuesday, U.N. Mideast envoy Robert Serry told the Security Council that the U.N. has received 13 reports of alleged chemical weapons use in Syria. He said Sellstrom’s team is studying this and other material.

“There is a growing body of limited but persuasive information showing that the regime has used and continues to use chemical weapons, including sarin,” said British U.N. Ambassador Mark Lyall Grant.

Russia, Syria’s close ally, has called the chemical weapon allegations facing Assad’s regime groundless, claiming Russian experts determined that Syrian rebels made sarin nerve gas and used it in the Khan al-Assal attack, in which 31 people died.

More than 93,000 people have been killed since the Syrian conflict started in March 2011, according to U.N. estimates.

(AP)