Washington, D.C. ? As people crowded into the capital for Barack Obama’s inaugural celebration, senior counterterrorism officials huddled in the White House situation room, frantically trying to unravel intelligence about a possible attack on Washington.

By Tuesday afternoon, as Obama took the oath of office, the threat of a terror plot by the Somalia-based al-Shabab organization had been debunked, but the flurry of activity underscored growing worries about this Islamic militant group.

“I think they are a serious problem, and I don’t think that we should be glib and take it lightly,” said Theresa Whelan, deputy assistant secretary of Defense for African Affairs. “Are they the ones that are going to plan the next major terrorist attack in the United States and carry it out? Probably not. But could they provide some of the foot soldiers for it? Yes.”

The State Department considers al-Shabab a terrorist organization with links to al-Qaida, something the group denies. Al-Shabab, which means “The Youth,” has been gaining ground as Somalia’s Western-backed government crumbles. The group’s goal is to establish an Islamic state in Somalia.