Israeli newspapers reported on the weekend that IS-linked websites claimed Gill Rosenberg, 31, was taken prisoner in Kobani after suicide attacks by members of the radical religious movement.
Other reports, however, said she was safe and sound in Rojava, the Kurdish-controlled region of northern Syria, where peshmerga fighters are holding out against IS.
"She is in Rojava and safe," Kader Kadandir, who said he is a member of a Kurdish group battling IS, wrote on Ms. Rosenberg’s Facebook page Sunday. He also posted several photographs of Ms. Rosenberg holding rifles and pistols.
A relative of Ms. Rosenberg said her family had not heard anything from her over e-mail and she had not signed into her Facebook page.
"She’s a very brave girl. She knew what she was doing. She did it for a reason. She knew the consequences," said the relative, who asked not to be identified.
A spokesman for the Department of Foreign Affairs and International Trade said the government is aware of the reports.
"Canada is pursuing all appropriate channels to seek further information," Nicolas Doire wrote in an e-mail.
Ms. Rosenberg, who lists White Rock, B.C., near Vancouver, as her hometown, has been living in Israel for several years. She gave a radio interview in Israel several weeks ago indicating she was planning to join Kurdish forces.