An eight-year federal investigation into terrorist recruiting yielded what authorities say is one of its biggest breakthroughs Monday, when six Somali-Americans from Minnesota were charged with planning to leave the United States and fight alongside Islamic extremist groups.

Two of the six were arrested by the FBI on Sunday in San Diego, where they intended to pick up passports and then cross into Mexico to board a flight to the Middle East, federal authorities said.

The other four were arrested Sunday by FBI agents at various locations across the Twin Cities.

All six were charged Monday with conspiracy to aid and support a terrorist organization, specifically the group calling itself the Islamic State in Iraq and the Levant (ISIL).

The two arrested in California are Mohamed Abdihamid Farah and Abdirahman Yasin Daud, according to court documents. The four arrested in Minneapolis are Adnan Abdihamid Farah, Hanad Mustafe Musse, Guled Ali Omar and Zacharia Yusuf Abdurahman.

It's not clear how the six men, who the Justice Department said range in age from 19 to 21, met or how well they knew each other, but it appears that their paths crossed again and again as they grew up in Minneapolis. After graduating from South High, Farah, Musse and Omar enrolled at Minneapolis Community and Technical College (MCTC). Farah and Musse majored in liberal arts; Omar was a pre-nursing student. Abdurahman, also a graduate of the Minneapolis Public Schools, enrolled at MCTC and studied computer support.

The arrests, which follow a 10-month investigation, indicate that young Somali men in the Twin Cities continue to be targeted and influenced by sophisticated recruiting campaigns carried out by ISIL, investigators said.

One of the men, in a conversation recorded by an FBI source, describes his disgust with living in the United States. "The American identity is dead. Even if I get caught, whatever, I'm through with America. Burn my ID," he said, according to a transcript filed with the case.

Help from informant

During the last two years, more than 20 Somali-Americans from Minnesota have left to fight alongside terrorists under the banner of ISIL, according to the FBI. Another four, also arrested while trying to leave, face federal prosecution in the Twin Cities under charges that they intended to fight for ISIL or the Al-Shabab terrorist brigade in Somalia.

The latest arrests underscore the depth of planning that such young men undertake to evade detection and get to the Middle East. Three of the six had tried leaving the United States once before, only to be stopped by FBI agents at JFK International Airport in New York and sent back to Minnesota. Another, Omar, has an older brother who left Minnesota in 2007 to join forces with Al-Shabab in Somalia.

"These men met regularly to plan their secretive trips," said Andy Luger, U.S. attorney for Minnesota, who announced the charges Monday. "These are focused men, intent on joining a terrorist group by any means possible."

The investigation also gave prosecutors and the FBI new insights into the informal, "peer to peer" nature of the recruiting network.

"There is no master recruiter in Minnesota," Luger said. "It may be their best friend right here in town. This group of friends recruited each other."

That informal structure made the network especially difficult to crack, according to FBI special agent in charge Rick Thornton. He and Luger said a major break in the case occurred when one of the original conspirators "had a change of conscience," and came to the FBI.

While the arrests came as a shock to many in the Twin Cities Somali community and the public schools, others had seen worrying signs.

Mohamud Noor, executive director of the nonprofit Confederation of Somali Community in Minnesota, said one of the men came into his office seeking help earlier this year.

"He had been interviewed by the FBI, and he said he and his friends had been followed for some time," Noor recalled, declining to say which of the men came in to see him.

The man was calm, Noor said, but said he was looking for legal representation and a better sense of what his rights might be. Noor referred him to a pair of nonprofits that provide free or low-cost legal assistance.

Recruiting from Syria

A criminal complaint released Monday said that Abdi Nur, a Somali-Minnesotan who made the trip from Minnesota to Syria last May, appears to be a key contact in the effort to recruit other young men from Minnesota.

Nur "remains in contact with individuals in Minnesota who aspire to travel overseas. From his locale in Syria, Nur recruits individuals and provides assistance to those who want to … fight abroad," according to an FBI agent's statement that outlines the facts in the complaint.

Another alleged conspirator of Nur, Abdullahi Yusuf of Inver Grove Heights, was arrested at the Twin Cities airport last May, a day before Nur flew to Turkey, where he was then planning to cross the border into Syria. Yusuf has pleaded guilty to conspiring to provide material support to ISIL, and Hamza Ahmed — who tried to fly from JFK — has been indicted on similar charges.

The pair arrested in California on Sunday were using nearly the same blueprint that four young men from the Twin Cities successfully employed in 2009 to avoid detection by FBI and airport security agents working undercover in U.S. airports. That group drove from Minneapolis to San Diego and then flew via Mexico to fight with Al-Shabab in Somalia.

The men arrested in California on Sunday left Minneapolis over the weekend, driving nearly nonstop to California, authorities said. They were tracked by FBI agents over the course of the road trip and then arrested when they arrived in San Diego.

The four arrested in Minneapolis were allegedly making their own plans to leave and were involved in the conspiracy to help their friends fly from Mexico, authorities say.

Reflecting on the arrests, Noor said Monday that he didn't hear again from the young man who came to him for assistance. Looking back, he says he would have engaged the man more "if I had the knowledge he was thinking of leaving to join ISIS."

Staff writer Mila Koumpilova contributed to this report.