There is no evidence that radicalized Somali American youths who have disappeared over the last two years are being trained abroad to attack the United States, intelligence and law enforcement officials told members of a Senate panel Wednesday.

Although worrisome, their apparent recruitment by the Shabab , a militant group linked to Al Qaeda, is more likely to signify that they are motivated to help their country fight against Ethiopians, who invaded the country in 2006.

"We do not have a credible body of reporting right now that leads us to believe that these American recruits are being trained and instructed to come back to the U.S. for terrorist acts," said Andrew Liepman, deputy director of intelligence at the National Counterterrorism Center. "Yet obviously we remain concerned about that, and watchful."

Liepman and others testified at a Senate Homeland Security and Governmental Affairs Committee hearing held to look into the disappearance of 12 to 20 young Somali Americans who are believed to be with the militant group.

Of particular worry is the recruitment of citizens who hold U.S. passports, which offer access to American soil and the ability to establish sleeper terrorist cells.

In October, suicide bomber Shirwa Ahmed, an American, took part in a series of coordinated attacks in Somalia. That, along with the disappearances from a closely knit Somali community in Minneapolis, has sparked concerns that the Shabab is targeting the area.

"What can we expect next?" asked Sen. Joe Lieberman (I-Conn.), committee chairman. "They could return to the U.S. at any time -- fully radicalized and trained in the tactics of terror -- to launch attacks here, bringing to our cities the suicide bombings and car bombings we have so far escaped."

Philip Mudd, an assistant director at the FBI, told the committee that the number of Americans thought to be recruited by the Shabab is relatively small.

"I would talk in terms of tens of people," he said. "It sounds small, but every terrorist potentially is somebody who could throw a grenade into a shopping mall."

Mudd also cautioned that the count may not be accurate, due to the reluctance of families to report missing relatives for fear they would be branded a terrorist and barred from returning to the U.S.

"I am sure there are people we are missing," he said.

A former United Nations advisor in Somalia told the committee that U.S. government silence on the 2006 Ethiopian offensive into Somalia inflamed anti-Americanism among many Somalis.

Some Somalis felt that the U.S. countenance of the Ethiopian invasion was retribution for the 1993 deaths of 18 U.S. soldiers there.

Kenneth Menkhaus, a political science professor at North Carolina's Davidson College said that for Somali militants, the final straw came in May, when an American airstrike killed the leader of the Shabab, seen as the main resistance group.

"Al Shabab announced that from that point, it would target all U.S., Western and U.N. personnel and interests," Menkhaus said. Although the Shabab has links to Al Qaeda, Menkhaus said the group sees the ties as a marriage of convenience.

"They are not as strong as they once were and likely to get weaker," he said.

rcole@tribune.com