(CNN) -- Press freedom advocates Reporters Without Borders expressed concern Monday about the fate of an Al Jazeera reporter arrested in Syria and reportedly deported to Iran, after Iran said it was unaware of her whereabouts.

Dorothy Parvaz disappeared after landing in the Syrian capital of Damascus on April 29 to cover that country's anti-government protests. The Syrian government announced last week that it had put her on a plane to Tehran on May 1 -- but Iran's state news agency IRNA quoted Foreign Minister Ali Akbar Salehi on Saturday as saying the Islamic republic had "no information" about her.

"The Iranian information ministry says it has no information about Parvaz," Reporters Without Borders said in a statement issued Monday. "If that is Iran's official position, it means she has disappeared. If not, we urge the Iranian authorities to say where she is being held, to allow her to leave the country or to account for the charges against her if they decide to continue detaining her."

The reported comments by Salehi were Iran's first comment on the case, Reporters Without Borders said.

Parvaz holds U.S., Canadian and Iranian citizenship. In a statement issued last week, Syria said the 39-year-old journalist was taken into custody after she arrived in Damascus with an expired passport and deported to Iran two days later.

Syria has been roiled for six weeks by anti-government protests and has largely prevented foreign journalists from covering the unrest. Media organizations have been relying on social media, eyewitness accounts and cell-phone video to report the story.

Thousands of supporters from around the world have started a social media campaign on Facebook, "Free Dorothy Parvaz" and Twitter #FreeDorothy in an effort to draw attention to her disappearance.

Dozens of international journalists have been detained and expelled from Syria since March 15, when anti-government protests began, said Mohamed Abdel Dayem, program coordinator for the Committee to Protect Journalists in the Middle East and North Africa.