Fourteen naturalized U.S. citizens have been indicted on multiple counts in connection with the conflict in Somalia, a law enforcement official told CNN on Thursday.
Most of those charged are believed to be outside the United States, with all of those perhaps in Somalia.
The 14 have been indicted on multiple counts unsealed on Thursday in three federal districts - Minnesota and the southern districts of Alabama and California. Two are under arrest and are believed to be in Minnesota.
The case has been going on for a few years and brings to 19 the total indicted on criminal charges, which include providing material support to a terrorist organization, the official said.
One of the key suspects is Omar Shafik Hamami, who lived in Alabama before going to Somalia.
Another source said the indictments allege that some people in the United States provided support to al-Shabaab, an Islamist group in Somalia that the United States has labeled as a foreign terrorist organization.
This comes a day after federal prosecutors in Chicago, Illinois, charged a U.S. citizen with trying to provide material support to two terrorist organizations - al Qaeda and al-Shabaab - and with another charge related to weapons of mass destruction, according to a criminal complaint.
Shaker Masri, 26, a U.S. citizen who lives in Chicago, was arrested Tuesday after he allegedly tried to violate a law that prohibits U.S. nationals "from using, threatening, attempting or conspiring to use a weapon of mass destruction outside the United States," the complaint said.
He had "advocated an extremist and violent interpretation of Islam" in conversations with a confidential source for federal investigators, according to the complaint. He told the source "that he wanted to participate in jihad" in Somalia or Afghanistan, it said.
The Minneapolis office of the FBI has been investigating about 20 men who have gone to Somalia in the past three years to fight with the Islamist extremist al-Shabaab organization in their East African homeland.
Federal officials previously indicted 15 Somali men from Minnesota on terrorism-related charges. Eight were indicted in November, joining seven who had previously been charged.
In addition to the Minnesota cell, the FBI says al-Shabaab has established operations in California, Ohio and Massachusetts. But Minnesota is home to the country's largest population of Somali residents, according to the Minneapolis Foundation, a philanthropic community organization.
Most of those Somalis came to the United States as refugees, the foundation says.
About one-third of Minnesota's Somali residents came directly from refugee camps. Others settled first in another state and then relocated to Minnesota.
Most go to Minnesota because an established Somali community already exists there, which means health care, education and other services are already in place to address the particular needs of Somalis. The availability of unskilled jobs that don't require English fluency or literacy also is a major draw.
Somalis in Minnesota primarily live in the Minneapolis metro area. Nearly one-third of Minnesota public school students who speak Somali at home attend Minneapolis schools.
Minnesota has seen an exponential growth of refugees fleeing war-torn parts of Africa, particularly Somalia, Liberia and the Sudan.
According to the Minneapolis Foundation, there were 5,000 Minnesota residents in 1990 who had been born in Africa. Ten years later, that number had grown to more than 34,000.
By 2002, nearly 9,000 more immigrants had arrived in Minnesota directly from various African nations.
The 2000 Census showed that 13 percent of Minnesota's foreign-born residents were from Africa - a higher percentage than any other state in the country.
- CNN's Jeanne Meserve and Susan Candiotti contributed to this report