(WASHINGTON) -- The nation's top law enforcement official suggested Thursday that the terrorist group believed to be behind the recent attack in East Africa could not pull off a similar strike inside the U.S. homeland.
Five days after terrorists launched a deadly assault inside a shopping mall in Nairobi, Kenya, Attorney General Eric Holder said the U.S. intelligence community still has not seen "any specific, credible evidence" that al Shabab, an Al Qaeda off-shoot based in Somalia, is planning to do anything in the U.S.
"I'm not sure they have the capacity to do anything in the United States," Holder added. "It doesn't mean, however, we will not take the threat that they pose...as a serious one."
A senior law enforcement official, speaking on the condition of anonymity, went further in assessing al Shabab's capabilities. The latest U.S. government analysis indicates that al Shabab does not have the capacity to strike inside the United States, despite any desires they may have, the official said.
In conducting their deadly missions, al Shabab is hoping to drive Western-backed forces – many of them from neighboring Kenya and Ethiopia – out of war-torn Somalia. So the terrorist group is focused on striking Western targets in Africa, not striking the U.S. homeland, the senior law enforcement official said.
In fact, the U.S. intelligence community has found "no specific, credible threats" indicating al Shabab is planning "any additional near-term, follow-on attacks" in East Africa, according to a joint intelligence bulletin issued by the FBI and the Department of Homeland Security earlier this week.
"The attack appeared designed to cause mass casualties and to gain media coverage by targeting a commercial facility frequented by Westerners as well as Kenyans," the bulletin said.
Meanwhile, agents from the FBI's New York Field Office landed in Nairobi on Thursday, joining other FBI personnel who were "on the ground since right after the incident began," as Holder described it.
FBI agents were able to access the attack site for the first time on Thursday, two sources briefed on the investigation told ABC News.
They will now work with their Kenyan counterparts to assess forensic evidence and determine whether any Americans were involved in the attack, according to Holder.
"We [currently] don't have any verifiable information that would indicate one way or the other way whether any Americans were involved," said Holder, speaking at an unrelated press conference in Washington.
For several years, Holder's Justice Department has been grappling with a stream of Somali-Americans, many of them from Minnesota, who were recruited to join al Shabab in Somalia. Justice Department officials have repeatedly expressed concern that such recruits could use their U.S. passports to re-enter the United States and launch acts of terror inside the homeland.
But many of the recruits have been killed on the battlefield overseas, and those who have returned to the U.S. are currently in prison. They have insisted they went to Somalia over a sense of Somali nationalism, not ill will toward the United States.
On Thursday, Holder did warn of one specific, credible threat to the U.S. homeland: the looming government shutdown.
Holder said the "stakes are high" and that the unavoidable furloughs inside the Justice Department "would be something very bad" due to the department's law enforcement responsibilities.
ABC News' Pierre Thomas asked Holder specifically, "Will Americans be less safe?"
Holder said his department "will do all that we can" and keep "essential" employees at work.
"But the reality is, we cannot do the job in the Justice Department as we would want to unless we have all of our people on the job," he said.
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