Egypt's Foreign Ministry says two Canadians released from an Egyptian jail after being held without charge for seven weeks may not be free to leave the country due to an investigation into potential charges.

John Greyson, a Toronto filmmaker and York University professor, and Dr. Tarek Loubani of London, Ont., were released from prison on the weekend following their arrest during anti-government demonstrations in Egypt in August.

The pair checked in for a flight to Frankfurt on Sunday, but were prevented from boarding the plane because their names appeared on a "stop list" issued by prosecutors, airport officials said.

The two retrieved their luggage and were free to leave the airport.

It was thought Greyson and Loubani would be free to return home sometime this week, but on Monday morning, CBC’s Middle East correspondent Sasa Petricic tweeted that may not be the case:

Greyson and Loubani, an emergency ward doctor, were arrested Aug. 16 during the violent demonstrations.

Petricic reported that the pair would have to wait until charges for all 600 protesters arrested with them are decided before leaving.

Could be a 'very long wait'

The lawyer for the two men plans to file a petition to remove their names from list of 600 under investigation for criminal charges so they can leave, Petricic reported.

"It’s not just a question of red tape as we were led to believe originally," Petricic reported Monday on CBC News Network. "They will not be allowed to leave … until the investigation is over.

"If that needs to run its course, it could be a very long wait even though they are now in a hotel room instead of a jail cell."

CBC Middle East correspondent Derek Stoffel also reported Monday that the setback could be a significant delay.

"Lawyer Marwa Farouk tells me the ongoing investigation could mean the men might have to remain in Egypt for some time yet," Stoffel tweeted on Monday.

Stoffel also reported that Farouk is hoping the prosecutor will make a decision before Thursday, when the Egyptian government will shut down for several days for a religious holiday.

Adria Minksy, a spokesperson for Lynne Yelich, Canada's minister of state for consular affairs, said: "We are aware of possible bureaucratic complications but Canadian officials continue to work tirelessly to facilitate Dr. Loubani and Mr. Greyson's departure from Egypt.

"We look forward to seeing these two Canadians return home shortly," said Minksy.

Marwa Farouk, who represents John Greyson and Tarek Loubani, says it could be a while before the two men are allowed to leave Egypt, even though they are no longer in jail. (Derek Stoffel/CBC)

Ferry De Kerckhove, Canada's former ambassador to Egypt, said Monday's news is a concern, but said he doesn't think Greyson and Loubani will be returned to jail.

“As long as they’re not indicted, I think eventually they will get free," he said Monday on CBC News Network.

"I remain hopeful that it is only a glitch," he said. “The longer it lasts, the more anxious it is for the family.”

Cecilia Greyson, the sister of John Greyson, said on CBC's Power and Politics with Evan Solomon that both men are in good spirits.

"Whenever I communicate with them and talk to them, they're both very happy and … they're so excited about coming back to Canada, they're actually not sleeping very well," she said. "John said he only slept two hours last night because he's so excited about coming back to Canada."

The two men's delayed departure is the latest twist in a struggle for their release that their friends and family have described as a "roller-coaster ride."

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

One day after after arriving in the country, the pair attempted to cross the border into Gaza. When they were turned back, they returned to Cairo, where protesters were swarming the streets demanding the release of ousted president Mohammed Morsi.

No charges laid

In a statement issued from prison last month, the men said they had decided to check out protests that were close to their hotel and saw at least 50 protesters killed. Loubani stopped to treat some injured protesters and Greyson filmed the carnage.

Their statement said that after leaving the scene of the protests, they asked police for directions and were stopped and beaten, and taken into custody.

Subsequently, Egyptian prosecutors accused them of "participating with members of the Muslim Brotherhood" in an attack on a police station, but never laid any charges.

Their arrest triggered a diplomatic push for their release from the Canadian government.

Last month, the Egyptian government announced the detention of Greyson and Loubani had been extended, raising worry among their friends and family.