MINNEAPOLIS >> One of two Minnesota men accused of planning to join the Islamic State group was stopped at an airport by FBI agents before traveling to the Middle East, but the other man slipped by authorities, according to a criminal complaint unsealed Tuesday.

Abdullahi Yusuf, 18, was stopped at the Minneapolis airport in late May after a passport specialist noticed he seemed nervous and didn’t have a specific itinerary, though he wasn’t arrested until Tuesday. Authorities are still looking for 20-year-old Abdi Nur, who left for Istanbul, Turkey, the next day and didn’t return in June as scheduled, according to the court documents.

Yusuf was arrested on his way to school at Inver Hills Community College. His attorney argued for his release during a Tuesday hearing in U.S. District Court in Minneapolis, noting he had been going to school and work despite knowing for months that he was under investigation. But a magistrate judge ordered him held until a detention hearing Wednesday.

Yusuf, who lives in Inver Grove Heights, a suburb of St. Paul, and Nur, of Minneapolis, are charged with conspiracy to provide material support to a foreign terrorist organization. Nur also is charged with providing material support to a foreign terror group.

U.S. Attorney Andy Luger said both young men conspired to join the Islamic State “to engage in a campaign of terror in support of a violent ideology.”

Authorities say a handful of Minnesota residents have traveled to Syria, which borders Turkey, to fight with militants within the last year. A total of 15 people have now been charged around the U.S. with offenses related to the foreign-fighter threat in Syria, according to the federal government.

Yusuf and Nur applied for expedited passports and, despite being unemployed, deposited about $1,500 for airline tickets into their checking accounts shortly before their scheduled departures, according to the criminal complaint.

Yusuf’s parents — who authorities said didn’t know about their son’s plans — attended Tuesday’s court hearing but declined to speak to The Associated Press.

According to the complaint, a passport specialist noticed Yusuf didn’t have a specific itinerary, the name of a hotel or details about a person he claimed he was going to see in Istanbul when he arrived at the airport on May 28. The specialist also noticed Yusuf became nervous, so alerted his supervisor, who went to the FBI.

Earlier that day, the FBI watched as Yusuf’s father drove him to school. About an hour later, Yusuf walked to a mosque, then was picked up in a car that authorities say Nur had been driving in recent days. Yusuf was dropped off at a light rail station, then went to the airport.

Authorities tried to find Nur after learning he was connected to the car. But the FBI learned on May 29 that Nur had left Minneapolis that day for Istanbul.

The criminal complaint said Nur had become “much more religious” in the two months before his departure and spoke about jihad. After he left for Turkey, a witness went to a mosque that Nur attended in Bloomington, a Minneapolis suburb, and confronted several people, according to court documents.

Investigators said Nur also had been communicating on Facebook with another Minneapolis man who authorities believe went to Somalia in 2008 to join al-Qaida-linked al-Shabab.