A Georgetown University student, along with two other American students, was arrested in Cairo Monday night.
Tahrir Square, the epicenter of the populist demonstrations this spring that led to the ouster of long-time Egyptian leader Hosnai Mubarak, has been engulfed in continuing political violence.
The three American students arrested by Egyptian security forces were attending the American University in Cairo, which sits on the edge of the square.
An official with the Egyptian Interior Ministry told the Associated Press the three students had been throwing firebombs off the roof of a school building at state security officers.
Georgetown University identified the student held as Derrick Sweeney, 19, of Jefferson City, Missouri. His mother described him as an idealist who got caught up in the democracy movement in Egypt.
The other two are Luke Gates, 21, and Gregory Porter, 19, both students at Indiana State.
Joy Sweeney, described her son as a principled person who stands up for his beliefs. He attended previous protests but stopped after a demonstration where dozens were killed, she said. He had assured his family the violence wasn't near him and he was safe.
Still, Joy Sweeney said she wasn't surprised he went.
"He got caught up in the whole college-change-the-world mentality, and he believes in democracy strongly," she said.
But she also said her son was the family peacemaker when siblings fought and she couldn't see him acting violently.
"I don't believe that he would intentionally throw a bomb at anyone," she said. "I don't believe that."
Their parents said Sweeney and Gates had been in Cairo since August, studying Arabic along with other subjects.
Joy Sweeney said others attending previous demonstrations had praised her son's Arabic and appreciated that a "blond-hair, blue-eyed kid" was supporting their calls for democracy.
The wave of protests and violence across Egypt that began Saturday has left 29 dead and thrown the country's politics into chaos less than a week before landmark parliamentary elections were to begin. Tens of thousands of people filled Tahrir Square on Tuesday to intensify pressure on Egypt's military leaders to hand over power to a civilian government.
Joy Sweeney and Gates's father, Bill Gates, they have been in contact officials from the U.S. Embassy but have little information so far about their sons.
"I don't think anybody really knows what to expect," Bill Gates said.
The U.S. Department of State said it was aware of the detentions of three U.S. citizens in connection with Tahrir Square protests and was seeking access.
Sweeney interned earlier this year with Rep. Blaine Luetkemeyer, a Missouri Republican. Paul Sloca, a spokesman for Luetkemeyer, said Sweeney worked in the congressman's Washington office from February to May, answering phones, attending meetings and completing duties typically assigned to an intern. Sloca said Sweeney was a nice person and a hard-worker.
"We're just hoping that he's safe and that he's being treated fairly," Sloca said.
A spokesman for the American University in Cairo said school officials have been in touch with the U.S. State Department and were reaching out to the students' parents.