Al-Jazeera television is demanding the immediate release of Canadian reporter Dorothy Parvaz, after learning that she is now in Iranian custody.

Parvaz travelled to Syria last month to cover ongoing anti-government protests, but was detained by authorities upon her arrival in Damascus nearly two weeks ago.

Al-Jazeera says it has since learned from Syrian authorities that Parvaz "is being held in Tehran."

The television network is still trying to get information from Iranian authorities about her whereabouts.

Al-Jazeera also published a statement from Parvaz's family, which also pleaded for her release.

"Dorothy is a dearly loved daughter, sister and fiancée, and a committed journalist. It is now nearly two weeks since she was detained. We appeal once again for Dorothy to be released immediately and returned to us," the statement said.

Fred Parvaz, the father of the detained journalist, told CTV News Channel on Wednesday morning that his daughter was born in Iran, but grew up in Canada.

He said he had not heard from Syrian or Iranian authorities about his daughter, though he has been in touch with the Canadian government about her case.

"I am very worried, I am very concerned and I just have to wait and see the new developments," he said by telephone from North Vancouver, B.C.

Today, Dorothy Parvaz holds Iranian, Canadian and American citizenship, the last being the result of having an American mother.

Her father said Parvaz has travelled to Iran on only one occasion as an adult, several years ago when she went on a sightseeing trip.

Parvaz has not made contact with Al-Jazeera since she departed for Syria on April 29.

The 39-year-old journalist previously reported for the Seattle Post-Intelligencer and joined Al-Jazeera last year.

Parvaz is a graduate of the University of British Columbia, though she also obtained a Master's degree from Arizona University. She also previously held journalism fellowships at both Harvard and Cambridge universities.

With files from The Associated Press and The Canadian Press