NAIROBI, Kenya (CNN) -- Sounds of heavy gunfire erupted from Nairobi's Westgate mall Tuesday, even as authorities said for the second day they had the building under their control.
The mall "is under the full control of govt forces and we are carrying out a sweep to ensure (it's) safe for everyone," Kenyan police tweeted Tuesday.
Kenya's Interior Ministry also gave reason for hope: "We're very near the end."
But four days after Al-Shabaab terrorists stormed the swanky mall, several gunmen -- including snipers -- were still inside, two senior officials said.
And it's uncertain how many hostages might still be trapped, although Kenyan officials tweeted early Tuesday that they believed all of them had been freed.
Hours later, the sound of an explosion was heard coming from the mall.
"We are doing cleanup of explosives that had been set up by the terrorists," police said.
At least 62 people were dead, the Kenya Red Cross said in its last accounting Monday. However, the death toll would not appear to include three Kenyan soldiers reported dead by the military Tuesday, and more bodies of civilians could remain inside the besieged mall.
And while the deadly siege drags on, the families of 65 people still unaccounted for don't know whether their loved ones escaped safely, are hiding somewhere in the vast mall or might be among the dozens killed by the terrorists.
Arrests at airport
Even as soldiers continued to sweep the mall, authorities also zeroed in on an airports and border crossings. More than 10 suspects were arrested Monday for questioning in relation to the attacks, the Interior Ministry tweeted Tuesday.
Authorities also increased security at all entries and exits across the country, the nation's Immigration Department said Monday.
Kenyan forces said they have killed at least three terrorists since the siege began Saturday. Three Kenyan soldiers are dead and eight others are being treated for injuries from the mall siege, the Interior Ministry tweeted Tuesday. Roughly 175 people have been wounded, officials said.
More than 200 civilians have been rescued, the military said.
Kenyan Foreign Minister Amina Mohamed told "PBS NewsHour" that some of the attackers had come from the United States. She said they were originally from Minnesota and Missouri, PBS reported Monday.
"As you know, both the victims and the perpetrators came from Kenya, the United Kingdom and the United States," Mohamed said. "From the information that we have, two or three Americans, and I think so far I've heard of one Brit" are among the attackers.
"The Americans, from the information we have, are young men, about between maybe 18 and 19, of Somalia origin or Arab origin," she told PBS. She offered no other specifics.
Gen. Julius Karangi, chief of Kenya Defense Forces, also said the attackers came from different countries.
"We have an idea who these people are, and they are clearly a multinational collection from all over the world," he told reporters in Nairobi. "This is not clearly a local event. We are fighting global terrorism here."
U.S. officials don't have any confirmation of Americans having been involved in the attack, deputy national security adviser Ben Rhodes said Monday.
Intelligence analysts were poring over electronic intercepts in an effort to verify the terror group's claims, two law enforcement sources told CNN.
Speaking Tuesday on CNN's "New Day," New York Police Commissioner Ray Kelly said he and other U.S. officials are concerned about the possibility of Americans going to Somalia, becoming terrorists and then returning home to engage in further mayhem.
"There is a fairly steady flow of young men, for the most part, wanting to go to Somalia, and the fact they could be trained and come back here and be used as a weapon is of great concern."
But he said he believed the risk of a Westgate-style attack in the United States remains low because of the work of the FBI and other law enforcement agencies to disrupt such plots before they can be carried out.
The terrorist attack began midday Saturday, Nairobi time, with an estimated 10 to 15 gunmen taking over the mall.
Witnesses said the gunmen went from store to store, shooting people, and then took hostages.
Survivor Bendita Malakia, a North Carolina woman who moved to Nairobi in July, told CNN affiliate WAVY-TV that she hid behind the closed metal gates of a store with dozens of others.
"While we were back there, you could hear them methodically going from store to store, talking to people and asking questions," she said. "They were shooting, screaming. Then it would stop for a while, and they would go to another store."
Al-Shabaab and some witnesses have said the attackers targeted non-Muslims.
Officials said most of the 62 dead are Kenyans. Six British citizens, two French nationals, two Indians and two Canadians, including a diplomat, also died, their governments said.
Those killed include:
• Dutch national Elif Yavuz, a senior vaccines researcher for the Clinton Health Access Initiative based in Tanzania. Yavuz was pregnant and expecting her first child in October, said Julio Frenk, dean of faculty at the Harvard School of Public Health. "Elif was brilliant, dedicated, and deeply admired by her colleagues, who will miss her terribly," the Clinton family said in a statement.
• Yavuz's husband, Australian-British architect Ross Langdon, who moved to Nairobi to build sustainable architecture for Africa, volunteering to build hospitals and clinics free of charge.
• Kofi Awoonor, a renowned African poet, author and Ghanian statesman. Awoonor earned his doctorate from New York's Stony Brook University and was a professor of literature there in the 1970s.
• A nephew of Kenyan President Uhuru Kenyatta along with the nephew's fiancee.
• A Peruvian doctor, Juan Jesus Ortiz, who had previously worked for the U.N. Children's Fund and lived in Kenya doing consulting work.
• Sridhar Natarajan, an Indian national and employee of a local pharmaceutical firm, and 8-year-old Paramshu Jain, the son of a bank branch manager, CNN sister network CNN-IBN reported, citing officials in India.
The Somalia-based Al-Shabaab terror group said on Twitter that it had sent the gunmen to the mall in retaliation for Kenya's role in an African Union military effort against the group, which is al Qaeda's proxy in Somalia.
Last year, the Kenyan military was part of a peacekeeping force that defeated Al-Shabaab forces to liberate the key Somali port of Kismayo.
The mall siege is the deadliest terror attack in Kenya since al Qaeda blew up the U.S. Embassy there in 1998, killing 213 people.
On Monday, Kenya's foreign minister told CNN it's clear that Al-Shabaab was not acting alone.
"This bears the hallmarks of al Qaeda," Mohamed said. "This is not just Al-Shabaab. In fact, the leaders are not Somali, as you may have heard. This was al Qaeda. It was a very well-coordinated effort."
But the attackers' national origins are irrelevant, she said.
"It doesn't matter where they come from. There are some Americans. There are some Brits. There are some others. It has nothing to do with the nationality of people. They are all evil, and we must deal with them as such."
-- CNN's Zain Verjee, Nima Elbagir, Arwa Damon and Victoria Eastwood reported from Nairobi. CNN's Atika Shubert, Michael Pearson, Becky Anderson, Lillian Leposo and Brian Walker also contributed to this report.
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