THE HAGUE, Netherlands (AP) — The director-general of the Organization for the Prohibition of Chemical Weapons has expressed confidence in a report into a deadly attack in Syria last year that has been called into question by a leaked letter.

Fernando Arias used his opening statement to the Conference of the States Parties on Monday to publicly support the report issued in March by an OPCW fact-finding mission that found "reasonable grounds" that chlorine was used in a deadly attack on the Syrian town of Douma.

The U.S., Britain and France blamed Syria and launched punitive airstrikes. Syria denied responsibility.

A letter purportedly by a member of the OPCW team and released by secret-spilling website WikiLeaks called its conclusions biased.

Arias says: “I stand by the impartial and professional conclusions reached by the fact-finding mission.”