The U.S. Federal Bureau of Investigation searched the office of a Minnesota travel agency this week for clues to the disappearance of 20 Somali-American men believed to be fighting in Somalia's civil war.

Omar Jamal, spokesman for the Somali Justice Advocacy Center, says the owner of Amana Travel was approached several months ago by two young men who wanted to travel to Somalia. Jamal says the owner, Ali Mohamud, refused to book the tickets when he learned the young men's parents were unaware of their plans.

But about 20 Somali-American men from the Minnesota area, including those two young men, have disappeared in the last two years.  They are believed to be in Somalia fighting with the Islamist militant group al-Shabab against the Somali government and its allies.

The U.S. considers al-Shabab a terrorist group.

One of the young men who disappeared, 19-year-old Jamaal Baana, was reported killed during fighting in Mogadishu, Somalia's capital.

A Somali-American man has already pleaded guilty in a U.S court to providing material support to terrorists, and another says he will plead guilty to the same charge.

Amana Travel owner Mohamud is facing separate charges of fraud and felony theft, for allegedly taking money for tickets he never bought and pocketing the refunds of tickets he canceled.

Large numbers of Somalis came to the United States after the fall of Somalia's last stable government in 1991.

Many of them settled in Minneapolis, a large city in Minnesota.

Some information for this report was provided by AP.