Two Minnesota men face criminal charges in connection with terrorist activities by the Syrian group ISIS, according to a federal criminal complaint filed in Minneapolis.

The document charges Abdi Nur, 20, and Abdullah Yusuf, 18, with conspiracy to provide material support to a designated foreign terrorist organization.

Yusef is under arrest and has an appearance in federal court Tuesday. Nur remains at large, authorities said.

"As charged, these two young men conspired to join ISIL and travel from Minnesota to the Middle East to engage in a campaign of terror," said Assistant Attorney General for National Security John Carlin, in a statement out Tuesday.

In an affidavit, FBI investigators pursued a report from a worker at a Minneapolis passport office, who became suspicious during an April interview about Yusef's application for an expedited passport for travel to Turkey.

According to investigators, Yusef had no firm travel plans, only a vague explanation of where he got the $1,500 application fee, and displayed suspicious behaviors as the application interview continued.

The FBI was called in because "the passport specialist found his interaction with Yusef so unusual," the affadavit said.

The FBI also had investigated Nur's request for an expedited passport, and found references on his social media about Jihad, and of seeing one of his contacts "in the afterlife."

Investigators said Nur had borrowed Yusef's car where authorities conducting a search later found documents that "provide further evidence of travel to Syria to join a terrorist organization."