Two Canadians being held in Egypt will remain detained for another two weeks.

An Egyptian prosecutor has extended the detention of John Greyson and Dr. Tarek Loubani by 15 days. The pair were arrested on Aug. 16 during deadly protests in the Egyptian capital of Cairo, but have yet to be officially charged.

According to an online message posted family member, Greyson and Loubani will be transferred from an overcrowded cell that holds 30 people to a cell that holds six.

“We are obviously extremely saddened to hear about the extension,” said Cecilia Greyson, John's sister, in a statement. “But just as importantly, we are now certain that John and Tarek’s detention is completely arbitrary, and the process they face lacks any semblance of fairness or credibility.

“While we have approached the Egyptian authorities in good faith and provided them with sworn affidavits, travel itineraries, and other particulars clarifying the nature of John and Tarek’s trip to Gaza, the Egyptian Prosecutor has alternatively missed and delayed important hearings into John and Tarek’s case and then extended their detention repeatedly without cause,” she added.

Greyson, who is a Toronto filmmaker and university professor, and Loubani, a doctor from London, Ont., stopped in Cairo on their way to Gaza, where Loubani was set to teach emergency-room medicine and Greyson was going to shoot a documentary.

Last week, major stars and filmmakers threw through support behind the two Canadians at the Toronto International Film Festival by releasing a statement signed by 311 artists, filmmakers, and academics from around the world calling for their immediate release.

A online petition that also calls for their release has received nearly 115,000 signatures.