Two Canadians being held in Egypt without charges have begun a hunger strike after learning they will remain detained for at least another two weeks.

Dr. Tarek Loubani and filmmaker John Greyson have informed friends and supporters through their Egyptian lawyers that they have begun refusing food to protest the arbitrary nature of their detention.

Greyson and Loubani were arrested on Aug. 16 during protests in the capital of Cairo, while transiting through the city on their way to Gaza.

They have been detained in Cairo’s Tora prison for the past 31 days without any charges. Egyptian officials have not provided any reason for the ongoing detention.

On Sunday, an Egyptian prosecutor said the pair's detention could be extended up to two years according to new emergency measures put in place in Egypt. Cecilia Greyson, John's sister, says the family was devastated to learn of the extension of the detention

"We had had some optimism that there might be some movement on the case this past weekend," she told CTV News Channel Monday. "We were hoping for their release."

She noted that the pair has grown frustrated with all the procedural delays. There have been problems with securing meetings between the pair's defence lawyers and the prosecutor, she said, and even presenting the prosecution with the visas and paperwork the pair had has not been enough.

"The prosecutor doesn't seem interested in the legal process. The prosecutor just seems to want to delay things," Cecilia said.

"So I think John and Tarek have felt that this is their only option. They're trying to take control of the situation as much as they can."

With the hunger strike, the pair is asking for either their release or at least better conditions. Cecilia says the pair was first held in a cell with 38 other people, with only one toilet and one tap for water. They now have cots to sleep in, but they have not been allowed outdoors in 30 days.

She says during the hunger strike, Loubani and Greyson plan to consume only juice and water, while doing what they can to maintain their health for as long as possible.

"Of course, Tarek is a doctor so I know they wouldn't have taken this on without really considering very carefully what the ramifications are," Cecilia said.

Greyson, a Toronto filmmaker and university professor, and Loubani, were headed to Gaza when they were arrest, where Loubani was set to teach emergency-room medicine and Greyson was going to shoot a documentary.

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

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

Mohammed Loubani, Tarek’s brother, said he and his family have been overwhelmed by the support they have received in their campaign to bring the pair home.

He added he's also grateful to the many Department of Foreign Affairs and Foreign Trade (DFATD) employees, and consular officials "who have worked so tirelessly to make sure Tarek and John stay safe and are returned to us as soon as possible."