Two Canadians released this weekend from an Egyptian prison have been barred from flying out of the country, CTV News has confirmed.

John Greyson, a Toronto filmmaker, and Tarek Loubani, a physician from London, Ont., checked in Sunday at the Cairo airport for a flight to Frankfurt, Germany, where they would have transferred to a flight to Canada, but were prevented from boarding because their names were on a "no flight" list.

Greyson and Loubani were released from prison on Saturday after spending seven weeks in custody. They were never formally charged with any crimes.

Greyson's sister, Cecilia Greyson, told CTV News Channel Sunday afternoon that Canadian consular staff had been working through "red tape" to complete the necessary paperwork to get her brother and Loubani out of the country.

She added that ongoing clashes in the capital of Cairo meant that her brother was still not out of harm's way.

"It's not a stable situation there. They are safe in a hotel at the moment but we won't breathe easy until they are out of Egypt and back home in Canada," she said.

Greyson also said that she believed it was pressure from the Canadian government that helped to secure the pair's release.

"I think the Ministry of Foreign Affairs worked very hard on our behalf and certainly, the very strong statement that (Foreign Affairs) Minister (John) Baird made at the beginning of the week saying that there would be consequences from the extended detention, I think that really did have an impact," she said.

Greyson says it might never be knows what finally compelled Egyptian officials to release the pair.

"I'm certainly grateful for the outcome but unfortunately I don't know what actually happened behind closed doors, and I'm sure we'll never know. But I'm grateful for the result," she said.

John Greyson, from Toronto, and Loubani, from London, Ont., had been in Cairo en route to Gaza on Aug. 16 when they were arrested during anti-government protests outside their hotel.

The pair said that Loubani had stopped to treat injured protesters while Greyson filmed the carnage. But Egyptian prosecutors alleged the pair had participated in the protests "with members of the Muslim Brotherhood."

The two were jailed with other inmates in a cockroach-infested prison cell as they awaited word on their fate, at one point staging a 16-day hunger strike to try to pressure Egyptian officials to release them.

Cecilia Greyson says she got word on Saturday evening in Halifax that "something significant was happening" with her brother. Then, around midnight Atlantic time, she got a call from her brother himself.

"He was in a hotel room at that point and wanted to let us to know that he was safe and they had been released. And so we were overjoyed," she said. "I couldn't believe that I was speaking to my brother; I hadn't spoken to him in 50 days."

Prime Minister Stephen Harper welcomed the news of the pair's release on Sunday. Speaking in Malaysia, Harper singled out the Canadian government's efforts to push for the men's release.

"The government of Canada has obviously been pushing for that and welcomes this decision by the government of Egypt," he said. "We look forward to seeing these two Canadian citizens return home in the not too distant future."

Harper later added he believed it was a "lack of clarity and co-ordination with Egyptian bureaucracy" that was preventing Loubani and Greyson from leaving Egypt.