A U.S. judge says a suburban Chicago man accused of seeking to join Islamic State militants in Syria will remain behind bars pending trial.

U.S. Magistrate Judge Susan Cox said at the end of a detention hearing Monday that the government demonstrated 19-year-old Mohammed Hamzah Khan is both a potential threat to the community and a flight risk.

Prosecutors say agents arrested Khan on Oct. 4 at O'Hare International Airport as he tried to board a flight to Turkey, which borders Syria.

Prosecutors also revealed for the first time publicly Monday that Khan's younger brother and sister were detained at the airport with him. Prosecutors said they also planned on joining the Islamic State, but they were never charged.