NAIROBI, Kenya - Kenyan President Uhuru Kenyatta says security forces have finally defeated a small group of terrorists after four days in fighting at a Nairobi mall.
In a televised address to the nation Tuesday, Kenyatta said "we have ashamed and defeated our attackers."
He said the attack had left 240 casualties, including 61 dead civilians and six of his security forces. He said five terrorists were killed and another 11 suspects have been taken into custody.
The president says three floors of the Westgate mall collapsed and that there are "several bodies still trapped in the rubble including the terrorists."
"Two or three Americans" participated in the attack on the Westgate Mall in Nairobi that has left at least 62 people dead and 175 injured, Kenyan Foreign Minister Amina Mohamed said.
A British woman was also among the alleged perpetrators tied to al-Shabab, the al Qaeda-linked rebel group that launched the attack on the upscale mall Saturday, Mohamed told PBS Newshour late Monday night.
She is the first official to allege publicly that U.S. nationals were involved in the attack. The FBI says it has been unable to verify that, and other Kenyan officials have said no women were involved, only men dressed as women.
The FBI is preparing to deploy a full team to Nairobi to investigate the Westgate Mall terror attack, officials told ABC News. Agents are coming from a variety of places but the case is being led by the New York field office, which handles crimes against Americans that occur in Africa.
The FBI investigates crimes against Americans and U.S. interests overseas. The United States offered assistance to the Kenyan government soon after the assault began Saturday.
"The West Gate Mall is under the full control of gov't forces and we are carrying out a sweep to ensure its safe for everyone," Kenyan police tweeted today on their official Twitter account.
Sporadic gunfire and explosions could be heard earlier Tuesday morning coming from the mall after Kenyan authorities said Monday they killed three suspected terrorists and arrested at least 10 others.
Kenyan police said the explosions resulted from their "doing clean-up of explosives that had been set up by the terrorists."
Officials said Monday they had rescued most of the remaining hostages inside the mall as forces went floor to floor searching for suspected terrorists associated with al-Shabab, an Islamist terror organization based in Somalia.
At least 62 people have been killed since the attack began Saturday when 12 to 15 al-Shabab militants wielding grenades and guns stormed the upscale mall and began firing on civilians. Eyewitnesses say the militants were shooting anyone who couldn't prove they were Muslim.
Arnold Mwaghacho, who was working at a gourmet burger bar when terrorists began their attack, was wounded in the attack and played dead so the militants would walk by his body.
"I took the blood that I was covered with. I rubbed it on my face so when they came there they think I'm dead," he said.
Among the dead are Australian architect Ross Langdon and his girlfriend, Elif Yavuz, a Harvard graduate who worked for The Clinton Foundation. Yavuz was eight months pregnant and was working with President Bill Clinton's foundation to fight the spread of malaria and AIDS in Africa.
At least 18 foreigners were among the dead, including six Britons, as well as citizens from France, Canada, the Netherlands, Australia, Peru, India, Ghana, South Africa and China.
President Kenyatta's nephew and the man's fiancée were also killed in the siege.
Al-Shabab, which means "The Youth" in Arabic, said the mall attack was in retribution for Kenyan forces' 2011 push into neighboring Somalia. In response, the group has increasingly set its sights on soft targets like the Westgate Mall.
The attack on the mall was the deadliest terrorist attack in Kenya since the 1998 al Qaeda truck bombing of the U.S. Embassy in Nairobi, which killed more than 200 people.
Al-Shabab has been among the most effective terror groups in attracting Americans to their cause, often of Somali descent, experts say.
"If you think about individuals who went and fought in a place like Somalia, and when they come back home there's nothing good that can come of this," terrorism expert Ali Soufain said. "And what we see today in
Somalia, it can be easily copied. What we see today in Somalia can be easily copied by people inside the United States."
U.S. officials estimate that as many as 50 Americans have been recruited to al-Shabab in the past six years, with more than half traced back to Minnesota's growing Somali community.
Kenyatta declared three days of national mourning.