Chicago ? Six of the 11 Egyptian exchange students who recently entered the United States and failed to show up for their college program were in custody Thursday after three more were arrested, officials said.

Police arrested Ahmed Mohamed Mohamed Abou El Ela, 22, at O’Hare International Airport after he tried to check in for a Chicago-to-Montana flight using an invalid ticket marked for a New York departure, Chicago police said.

El Ela raised his voice and became unruly after an employee at a Delta ticket counter refused to let him exchange the ticket for a valid one, said Timothy J. Bolger, the Chicago police officer at the scene.

After federal officials confirmed El Ela was one of the students they were seeking, police turned him over to immigration agents, Chicago Police Supt. Phil Cline said.

Two other students, El Sayed Ahmed Elsayed Ibrahim, 20, and Alaa Abd El Fattah Ali El Bahnasawi, 20, were arrested at a residence in Dundalk, Md., outside Baltimore, by U.S. Immigration and Customs Enforcement agents, the FBI said.