There are still plenty of unanswered questions about al-Shabaab's weekend attack and siege at an upscale Nairobi mall. The death toll stands at 67 people as the search for victims continues.

While Kenya's foreign minister said two or three of the attackers – estimated at 10-15 in total – were Americans, U.S. officials say that remains unconfirmed. Twenty FBI agents are in Nairobi to help in the investigation. Whether Americans were part of the slaughter or not, the attack has some officials concerned that the al-Qaida-affiliated Somalia-based terrorist group is taking its jihad internationally.

The Kenya attack is seen as retaliation for the country's help in fighting al-Shabaab in Somalia. The United States has financed those operations with hundreds of millions of dollars, so "there is growing fear that the group could turn its sights on American interests more directly," the New York Times reports. With more than two dozen Somali-Americans believed to be in its ranks, there are concerns some might try to return to the United States and plot attacks here. Or, al-Shabaab could just target American interests in Africa, where American businesses have a growing presence and where American tourists are drawn.

In an interview with the Daily Beast's Josh Rogin, Somalia's President Hassan Sheikh Mohamud said al-Shabaab may be based in Somalia, but it has "an international agenda."

"It can happen here in the United States as it is now happening in Nairobi," Mohamud said.

The question of al-Shabaab's ability to strike American interests is not new. A House Homeland Security Committee staff report in 2011 said the group poses "a direct threat."

But not everyone buys that. House Foreign Affairs Committee Chairman Ed Royce, R-Cal., said there's no evidence indicating that al-Shabaab could attack within the United States despite the presence of Americans inside the group.

Similarly, House Armed Services Committee Chairman Mac Thornberry, R-Texas, told The Hill that al-Shabaab is "on the verge of being defeated" despite the audacity of the Nairobi attack. "When you pin a rattlesnake into a corner, they are going to strike out," Thornberry said.

Mohamud agreed, but said al-Shabaab remains a danger.

"They are on the run," he said. "But their threat is not yet finished. They have still training camps. They have bomb factories in very remote areas… Even if we defeat [Shabaab] militarily completely, that's not the end of the war with [Shabaab]. They will continue suicide bombs, roadside bombs; this will go on for some time."