Three U.S. students who were detained for allegedly throwing firebombs at police have been released without charge and are heading home.

Update at 9:21 p.m. ET: The first student has left Cairo, the Associated Press reports.

Luke Gates, 21, who attends Indiana University, took an early Saturday flight to Frankfurt, Germany, the first stop on his trip home to Bloomington, Ind.

Derrik Sweeney, 19, a Georgetown University undergrad

from Jefferson City, Mo., and Gregory Porter, 19, of Glenside, Pa., who attends Drexel University, are expected to follow.

Original post: Three American students arrested during a protest in Cairo have been released and are preparing to leave Egypt, the mother of one tells the Associated Press.

They are to fly from Cairo to Frankfurt, Germany, late tonight U.S. time, said Joy Sweeney of Jefferson City, Mo., whose 19-year-old son, Derrik, was arrested late Sunday with two companions from American University for allegedly throwing firebombs at police during protests in Tahrir Square. The others are Gregory Porter, 19, of Glenside, Pa., who attends Drexel University; and Luke Gates, 21, of Bloomington, Ind., a student at Indiana University.

Sweeney, a student at Georgetown University, will then fly to St. Louis, via Washington, and is to arrive home late Saturday and a belated Thanksgiving dinner, his mother said.

Cairo's top prosecutor said security forces had found a bag containing empty bottles, gasoline, a towel and a camera with the three Americans, who said the bag belonged to two friends.

BLOG: 3 U.S. students accused of firebombing Egyptian police

Earlier today, Sweeney's father, Kevin, told CNN that his son had been falsely accused and that he was merely "observing something that was definitely a phenomenon of the culture."