Organizers of the Toronto International Film Festival expressed grave concern Thursday about the disappearance of Syrian documentary maker Orwa Nyrabia, calling it an arrest. The director of DOX BOX, an international documentary film festival in the Syrian capital, was at a Damascus airport August 23 for a flight to Cairo when his family lost contact with him, an activist group said last week, citing his family. The activists said that, according to EgyptAir, he did not board the plane, indicating he had been arrested by Syrian authorities. It was not possible to confirm the claim. "We are extremely concerned by his arrest -- filmmakers must be allowed to express themselves through their films, without fear of reprisal," organizers said in a statement. The acclaimed filmmaker has produced documentaries in Syria, most notably for the Franco-German television channel Arte, and served on the juries of a slew of other documentary film festivals. He studied film production at the Sorbonne in France. "Nyrabia belongs to the emerging generation of Syrian filmmakers passionate about world cinema and passionate about freedom," the organizers said.