Cairo (CNN) -- It was the happiest of homecomings. Ecstatic family members and friends embraced Muhammad Radwan when he emerged from Cairo International Airport safe and sound. They laughed, cried and even danced to the music of a traditional Egyptian band outside the airport doors.
For an entire week, Radwan's loved ones tried to fight off fears of torture or worse after he made an unexpected appearance on Syrian state television in what appeared to be a videotaped interrogation. The anchorwoman called it a "confession" by a foreigner who had been "paid to destabilize Syria."
In the report, Radwan sat frightened on a couch, telling an interrogator standing off-camera that he had traveled to Jerusalem and that he had communicated via e-mail with a Colombian journalist who offered him the equivalent of $18 for photos from Syria.
Within hours of Radwan's television appearance, his father Abobakr rushed to Syria to plead for his son's release.
"Knocking on the doors of the Syrian officials, whoever they were ... asking anything about Muhammed. And it was total darkness," the elder Radwan recalled.
Houston-born Radwan is not the only American citizen to disappear into Syria's repressive security system during a bloody crackdown on anti-government protesters that has led to the deaths of more than 100 people.
Pathik Root, 21, spent 15 days in a Syrian prison recently.
"They originally picked me up because they saw me with my BlackBerry out about a hundred yards from what ended up being a protest," Root said in an interview on Monday with CNN's Elliot Spitzer, after he returned to the U.S. from Syria last weekend.
The Middlebury College junior had been studying abroad in Damascus, a popular destination for foreigners seeking to learn Arabic. Instead, he witnessed torture carried out against other prisoners in a crammed detention facility.
"About 75% of the other prisoners I met were beaten pretty brutally to the point that I caught a glimpse of blood-soaked rags once. One person's foot was beaten till their toenail fell off. There were brutal interactions between the guards and the prisoners, including electrocution and who knows what else," Root said.
Though packed with at least 15 other detainees in a 10-by-12-foot cell, Root said he was probably spared any beatings thanks to his American citizenship. However, he was also denied any communication with the outside world.
"You're supposed to be able to call your consulate and actually have consular visits, neither of which they offered to me," Root said.
The U.S. Embassy in Damascus confirmed there is another American male missing and currently believed to be in Syrian custody.
"The Syrian government has not given official notification of his detention or his consular access, and in this they are violating the Vienna Convention on Consular Access," wrote embassy spokesperson Angela Williams in an e-mail to CNN.
Human rights groups report more than 100 people have been killed in Syria since anti-government protests first erupted there last month.
According to the New York-based human rights monitor organization Human Rights Watch, more than 500 people, almost all of them Syrians, have been detained during this period. At least 150 of those detainees have been released, said Nadim Houry, Human Rights Watch's Syria researcher.
"Syria's security services regularly hold detainees incommunicado -- cut off from all contact with family, a lawyer or any other link with the outside world -- for days, months and in some cases, years," Human Rights Watch wrote in "A Wasted Decade," a recent report on Syrian President Bashar al-Assad's first 10 years as president.
The report also documented "a frequent pattern of torture and other ill-treatment by Syria's security services of political and human rights detainees as well as criminal suspects."
Muhammad Radwan, a 32-year-old dual national Egyptian-American citizen, said he was not physically abused during his weeklong detention. But at dark moments, he admitted to wondering whether his parents would still be alive if and when he was released.
"You think about worst-case scenarios when you have a lot of time," Radwan said, glancing at his father. "What could happen if I eventually get out of here and not everyone is around?"
Speaking to CNN after his return to Cairo, Radwan downplayed his incarceration. He personally thanked al-Assad for intervening to ensure his release, describing the entire experience as a "misunderstanding."
Radwan was fortunate. Supporters organized "Free Radwan" protests at Syrian embassies in the U.S., Great Britain and Egypt. High-ranking Egyptian and American officials also intervened on his behalf.
CNN's Leinz Vales contributed to this report.