The midwestern U.S. state of Minnesota is home to an estimated 70,000 Somali immigrants. It is one of the largest Somali populations outside of Africa, made up mostly of refugees who fled decades of war in their home country. But in recent months, a number of young Somali men have disappeared, and the U.S. Federal Bureau of Investigation believes some of them went to Somalia to fight with the Islamic extremist group, al-Shabab.

Although some U.S. media are reporting that a few of the Somalis have recently returned to Minnesota, the disappearances are a troubling development for law enforcement agencies and a shock to the community where many of the young men grew up.

In February, the FBI reported that 27-year-old Shirwa Ahmed, a naturalized American citizen from Minneapolis, was the prime suspect in an October suicide bombing in Somalia.

But his case may not be unique. FBI agent E.K. Wilson in Minneapolis is investigating the disappearance of more than a dozen other young men who left Minnesota late last year, around the same time Shirwa Ahmed was last seen alive in the U.S.

"If in fact he turned out to be involved in the suicide bombing, it would, to the best of our knowledge, be the first time that an American citizen was involved in a suicide bombing overseas," Wilson says.

The incident shocked the Somali community in Minneapolis and raised concerns about the activities of the other missing men. Abdirahman Mukhtar is the youth program manager at the Brian Coyle Center, situated in a poorer residential area that is home to thousands of Somalis. He went to school with Shirwa Ahmed.

"He graduated a year ahead of me, but I knew him as a very nice guy, a very quiet guy."

Mukhtar knew some of the other missing young men. He says none gave any hint of where they were going, or why.

"Some of the community members don't believe this really happened, actually," he says. "So if it happened, this is still something that is against our culture and our religion, which is Islam. This is something new to our community."

The FBI believes the missing men were recruited by the Somali insurgency group al-Shabab. The United States considers al-Shabab, which in Arabic means "The Youth," as a terrorist organization.

Many of the missing men now being investigated by the FBI regularly attended prayer services at the Abubakar As-Saddique Islamic Center. Omar Hurre is the executive director of the center and knew some of them. He says one reason they may have returned to Somalia is that they were caught up in the outpouring of nationalistic fervor following Ethiopia's invasion of the country in 2006.

"It was kind of popular within the Somalis that many people were calling to liberate the country from the illegal occupation," Hurre says. "Some of the factions who were fighting over there came even over here to the Minneapolis-St. Paul area and held some conferences, some rallies, and sometimes openly calling people to fight in Somalia."

Hurre emphasizes that regardless of the motive, if the actions of the young men prove to be true, they have violated the trust of the community and the teachings of Islam.

"Using suicide bombings is clearly anti-Islam, and it's not in any way allowed in the Islamic religion. It is also new to the Somali culture, because this is the first time we have heard that Somalis are using suicide bombings to achieve some political goals."

Agent E.K. Wilson says finding the other missing men is a top priority for the FBI.

"Any time you have a number of men, children in some cases, vanish, given the circumstances they are returning to and the potential for harm to them or others, it is a significant investigation."

A grand jury is also investigating the disappearances. Several members of the community, including those who worship at Abubakar As-Saddique, have been issued subpoenas to testify.