By Mark Hosenball
WASHINGTON (Reuters) - U.S. authorities are urgently looking into information given by the Kenyan government that residents of Western countries, including the United States, may have been among armed militants who attacked a Nairobi shopping mall over the weekend, killing at least 62 people, U.S. security sources said.
Kenyan officials said their forces were "in control" of the mall and combing it floor by floor looking for anyone left behind. They said they believed all hostages had been freed.
A U.S. national security source said that the United States had been notified through official channels that Kenyan authorities now believed that foreigners, likely including U.S. citizens or residents, were among the gunmen who attacked the mall.
Reuters on Monday quoted Julius Karangi, Kenya's chief of general staff, saying that the attackers included gunmen from several countries. "We have an idea who they are, their nationality and even the number," Karangi said.
He added: "We also have an idea this is not a local event. We are fighting global terrorism here and we have sufficient intel (intelligence) to suggest that." Karangi said the attackers were "clearly a multinational collection from all over the world."
The U.S. national security source said that Kenyan authorities had passed similar information to American authorities but that it was still unclear how much hard evidence the Kenyans had.
A European security source said that Western authorities still had reason to be wary of claims by Kenyan officials of foreign involvement in the attacks.
U.S. officials had been looking for evidence that U.S. citizens or residents were involved in the attack at least since Sunday, when a Twitter account purporting to represent the Somalia-based militant group al Shabaab published what it said were the names of three Americans, a Canadian, a Swede, two Britons, and a Finn who participated in the attack.
Multiple U.S. security sources said U.S. investigators now believe the Twitter account and its claims were bogus.
However, U.S. authorities acknowledged that over the past several years, as many as several dozen Americans have traveled to Somalia to train or fight with al Shabaab, many of them from Somali exile communities in Minneapolis-St Paul, Minnesota.
Laith Alkhouri, a private expert who monitors militant Internet sites, said that al Shabaab would gain various advantages by using Western or U.S. residents to carry out operations.
"For Shabaab, it helps having Western nationals as operatives: they carry Western passports, allowing them to travel more freely, under less scrutiny. They also attract worldwide attention, making Shabaab, in the eyes of the jihadist base, a highly credible al Qaeda branch on the same footing as AQAP (Al Qaeda in the Arabian Peninsula), for attempting and succeeding to carry bold transnational operations," he said.
(Editing by Alistair Bell; Editing by Sandra Maler)