A group of Canadian writers and filmmakers is demanding the release of two Canadians detained in Egypt since Aug. 16. 

The artists, including filmmakers Atom Egoyan and Sarah Polley and writer Michael Ondaatje, issued their demand Tuesday at a news conference at the headquarters of the Toronto International Film Festival.

Tarek Loubani, a doctor from London, Ont., and John Greyson, a Toronto filmmaker and university professor, were arrested on Aug. 16 amid deadly riots in Cairo. They have yet to face any formal charges.

Loubani was in Egypt to train emergency doctors in Gaza, and Greyson was there to observe and document that work.

At Tuesday's news conference, a letter signed by more than 300 artists and actors, including Ben Affleck, Alec Baldwin and Frances McDormand, was released. There is also an online petition with more than 100,000 signatures demanding the men be set free.

In addition to demanding the release of the two Canadians, the artists who spoke said the arrest of the men is an affront to the principles of freedom of speech and expression, values held dear by those who participate in TIFF.

Egoyan, who has known Greyson for 30 years, said there's no reason for the men to be detained.

"We’re demanding that he be released and be allowed to do what he does best, which is express his profound humanitarian concerns," said Egoyan. "This is about the freedom of expression and that he was trying to tell a story and was stopped. We are very worried about both of them."

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Filmmaker Sarah Polley spoke Tuesday, calling on the Egyptian authorities to release detained Canadians John Greyson and Tarek Loubani. (Jessica Wong/CBC)

Greyson sister's Cecila said her brother and Loubani were simply in "the wrong place at the wrong time."

She also pointed out that no formal charges have been filed against the two men.

Ondaatje also spoke Tuesday, and said writers must defend the right of other writers and journalists to work in dangerous parts of the world.

"Writers and artists travel to dangerous places in the real world, as well as in their imaginations," he said. "To support this work, we have to defend [their] freedom to do so."