Dorothy Parvaz called her fiance on April 28 and told him something he didn't want to hear: She was going to Syria to report on the uprising and the government's ruthless efforts to quash it.

The Iranian-born Al-Jazeera reporter, who spent her teen years in Canada and studied and worked in the U.S., had been in challenging situations before, including returning to the land of her birth to report on changes there for a U.S. newspaper. But nothing in her reporting history compared to the crackdown in Syria, where many reporters had already been detained or expelled by the time she set off.

"Nothing I could say would change her mind," said her fiance, Todd Barker, who was driving from Arizona to Los Angeles that night. "I could tell by the tone of her voice that it was gonna happen. She is very committed. She believes reporting the truth is a force to make people's lives better and she lives and breathes that."

The next day, Barker heard nothing from his fiancee, whom he normally communicates with several times a day.

"I went to bed on the 29th and I couldn't sleep," he said. "I had this horrible feeling in the pit of my stomach. And then I got the call from Al-Jazeera at 3 a.m. It was like a nuclear bomb exploding in your life."

Parvaz hasn't been seen or heard from since she left Al-Jazeera's headquarters in Doha, Qatar, on April 29. On May 4, Al-Jazeera said Syrian authorities confirmed she was detained.

On May 10, Syria said she had not been in the country for more than a week. A day later, the government said she had been deported to Tehran, Iran, following her detention in Damascus, the Syrian capital. There has been no comment from Iranian officials.

Parvaz has Iranian, Canadian and U.S. citizenship. She used her Iranian passport to enter Syria because she couldn't enter with either of the others.

"The details of what's happened to her are not clear at all," said David McCumber, who worked with Parvaz for more than 10 years when he was the managing editor at the now-defunct Seattle Post-Intelligencer. "But Dorothy is enormously resourceful. If anyone could handle a situation like this, it would be her."

Parvaz, 39, is among at least five journalists Syria is holding, according to the Committee to Protect Journalists. Others include Ghadi Frances, who writes for the Lebanese daily As-Safir; Al-Arabiya correspondent Mohamed Zayd Mastou; and freelance photographer Akram Darwish. Sara and Mastou were first detained more than a month ago, CPJ said.

"Damascus must account for all detained journalists and release them immediately," said Mohamed Abdel Dayem, the group's Middle East and North Africa program coordinator.

CPJ said that since the social unrest erupted in Syria in March, about 20 local and international journalists have been physically assaulted, detained or expelled.

Syria has imposed a media blackout intended to limit coverage of the unrest by refusing to issue visas to foreign journalists and preventing access to trouble spots. President Bashar Assad — and his state-run media — have blamed the unrest on terrorist groups and foreign agitators.

Two Associated Press journalists were expelled from the country with 45 minutes' notice. Five Reuters journalists also faced detention and intimidation, including one who was expelled by Syrian authorities on March 25 after five years as the agency's correspondent in Damascus.

If Syria has sent Parvaz to Iran, that could reinforce allegations that Iranian authorities are working closely with Assad's government to crack down on protesters and choke off independent media coverage.

A statement by Al-Jazeera urged Iranian authorities to provide details on Parvaz, who works for the news network's English-language channel. The network said it is "deeply concerned" for Parvaz's welfare.

The State Department in Washington also expressed concern and said it was striving to get further details. Department spokesman Mark Toner said U.S. officials were seeking assistance from Swiss diplomats who represent U.S. interests in Iran.

Parvaz's work has taken her to Qatar, Iran and most recently to Japan to report on the aftermath of the earthquake and tsunami for Al-Jazeera. She also won a prestigious Nieman Fellowship in 2009, spending a year at Harvard University before moving to Britain, where she earned another fellowship at Cambridge, where she focused on the media and Iran.

Her American mother and Iranian father divorced when she was 5, and she left Iran at age 10 in 1981, two years after that country's revolution. She lived for a time in San Diego with her mother, but eventually moved with her father, Fred Parvaz, and stepmother, who had immigrated to British Columbia.

"We are close," said Fred Parvaz. "Very close. She wanted to come to Canada because she didn't want to be apart from me."

Growing up in a bedroom community in North Vancouver, Dorothy wrote for her high school literary magazine.

She was "interested in world events and making sure those around her knew what was going on," said childhood friend Sheelagh Brothers. "She was somewhat quiet around others, unless she felt that they were being ridiculous, in which case she let them have it, with sometimes biting, witty comments."

Fred Parvaz said his daughter came home from high school one day and told him she was going to be a journalist.

"I asked her to consider other options because it's hard to get a job as a journalist. But there's no changing her mind when she decides something. I'd like to say that determination is genetic," he says.

Dorothy Parvaz earned an undergraduate degree in English literature from the University of British Columbia, then headed to Japan to work for the English edition of the Asahi Shimbun. She later completed a master's degree in journalism at the University of Arizona before moving to Seattle, where she worked for The Seattle Times and then for the Post-Intelligencer before it folded.

One month after the Sept. 11, 2001 attacks, she donned a hijab — something she hadn't worn since she was a girl — for a story for the Post-Intelligencer. She reported on how much differently she was treated as she walked around Seattle wearing the traditional Muslim headscarf, and wrote about being not only a Muslim, but the only practicing Muslim in her family.

"It was her idea, something she wanted to do," McCumber said. "I was proud of her for having the idea and the courage to execute it, and I thought she did an excellent job."

In 2006, Parvaz went to Iran on her own time to report on how her birth-country had changed since the revolution. McCumber said she produced "a magnificent series of stories" on her experience.

Yasmine Ryan, a friend and Al-Jazeera colleague, said she wasn't surprised that Parvaz wanted to report from Syria. "She seemed a little nervous on the eve of her trip but was still joking around as usual," she said.

"It's an awful feeling having someone you know just disappear. Something you hear about and report on a lot about as a journalist, but not something you expect to experience firsthand," Ryan said.

Barker, the Parvaz family, colleagues and friends have been steadfastly campaigning for her release.

Parvaz's detention has highlighted the worsening relations between Syrian authorities and Al-Jazeera. Its reporters had been allowed to stay in Syria as other reporters were expelled, but two weeks ago the station said it was scaling back its Syrian operations, citing harassment by security forces.

Elsewhere as unrest sweeps the Arab world, regimes struggling to hold onto power have waged widespread crackdowns on the media.

In Libya, foreign journalists working in the capital Tripoli are under strict controls by forces loyal to Moammar Gadhafi, and several have been detained. In the Gulf state of Bahrain, opposition media have been closed and journalists and bloggers arrested as the U.S.-allied monarchy tried to muzzle dissent.