TUCSON - A federal grand jury Wednesday indicted two Syrian men on charges of impersonating U.S. citizens after Border Patrol agents stopped them in southern Arizona and found an undocumented Mexican immigrant in their car. According to a criminal complaint, Ala Salem Mamoud Al-Kurdi and Mohamed Tamman Nakchgandi, both citizens of Syria, were pulled over by Border Patrol agents on Feb. 18 on Arizona 86, a highway that runs through the Tohono O'odham Nation, a vast reservation southwest of Tucson. In the back seat of the Cadillac, driven by Kurdi, agents spotted a Mexican man who later admitted to crossing the U.S.-Mexican border illegally three days earlier, according to Border Patrol reports. Kurdi and Nakchgandi, the passenger, said they were naturalized U.S. citizens born in Syria, but agents found they were in the country illegally, according to court records. The agents reported that a second Cadillac was spotted traveling in tandem with Kurdi's along the highway, but got away. The Mexican man later told authorities he crossed the border with five other undocumented immigrants, who were in the second car, the Border Patrol reported. A check of immigration records showed that Nakchgandi had entered the country legally in 1999 with a temporary visitor's visa, but overstayed, according to the Border Patrol. The agency reported that Kurdi also entered legally with an employment-authorization card that recently was canceled. Kurdi, 25, and Nakchgandi, 24, were each charged with impersonating a U.S. citizen. Authorities have not established a link between the pair and the undocumented Mexican man, "except that they were all in the same vehicle," according to the Border Patrol. An arraignment for Kurdi and Nakchgandi is scheduled for Thursday in U.S. District Court in Tucson, said Sandy Raynor, a spokeswoman for the U.S. Attorney's Office. The two men are being held in federal custody until trial, according to court records. Their attorneys did not return phone calls Thursday.