Al Jazeera is reporting that one of its correspondents, Dorothy Parvaz, has gone missing in Syria. Parvaz, who holds American, Canadian, and Iranian citizenship, landed in Damascus on Friday and has not been heard from since. Business Insider reports that "she never checked into her hotel, leading some to believe she is being held at the airport."

Parvaz, 39, has been with Al Jazeera since 2010. Previously she was a reporter with the Seattle Post-Intelligencer. Parvaz is only the latest journalist to be detained by Syrian authorities; Mohamed Abdel Dayem of the Committee to protect Journalists estimates that there are "between a handful and a dozen" journalists in similar straits. Dayem has also said that "Dorothy's detention is really just the latest episode in an effort by the Syrian government to institute a media blackout."

Many of those detained have since been released: Amer Matar of the Arab newspaper Al-Hayat was let go in April after about 19 days in custody, and Reuters correspondent Suleiman al-Khalidi was released last month after being held for three days. But the French journalist Khlaed Sid Mohand, arrested in Damascus on April 9, is still missing.

There's already a Twitter hashtag devoted to Dorothy Parvaz, and a Facebook page calling for her release. Larry Johnson, Parvaz's former colleague at the Post-Intelligencer, has said that "the Syrian government has not responded at all, which is why people need to flood the Syrian embassy in D.C. with calls and emails. That sort of thing does work."