The FBI is investigating whether as many as five Americans were among the small team of terrorists who took over a Kenyan mall and launched a bloodbath that has left at least 68 dead and 175 injured over two days of carnage.
The investigation is in its early stages and until a conclusion of the siege in Kenya — which spilled into a second bloody day on Sunday — authorities may not know for sure whether any U.S. residents were involved.
The notion that Americans were involved came directly from the terrorists themselves — or at least a Twitter feed purporting to represent the Somali al-Qaeda affiliate al-Shabab, which has claimed responsibility for the mall attack.
The account listed specific names and home states of the Americans they said were on their side. The group has had several Twitter handles shut down over the course of two days as they blast pro-jihad propaganda across the Internet.
Two of the purported American jihadists are allegedly from the St. Paul-Minneapolis community in Minnesota, which authorities say is the largest Somali population outside of Mogadishu, with some 85,700 members, according to latest the Census Bureau numbers.
The FBI and local authorities should be able to determine quickly if the alleged suspects are at home, and fairly quickly if they may have been radicalized and perhaps gone over seas. But if the individuals have moved overseas, their leanings will be much harder to figure out.
Meanwhile, an unknown number of people were still being held hostage Sunday by the masked gunmen who stormed the Nairobi mall Saturday afternoon in Kenya and indiscriminately shot anyone not of Muslim faith
Kenya's military said on Sunday it had freed most of the hostages from the mall after a major push to take back the shopping center.
"Most of the hostages have been released, and the Kenya Defense Forces has taken control of most parts of the building," Kenyan military spokesman Colonel Cyrus Oguna told the television station KTN.
He did not say how many hostages had been held or freed.
In an effort to end the two-day siege, Kenyan officials had announced late Sunday that they plan to launch a “major” assault against the attackers still inside the upscale Westgate mall.
The militant Islamic group al-Shabab, based in neighboring Somalia, claimed responsibility for the attack via Twitter, saying it was in retaliation "for the lives of innocent Muslims" killed by Kenyan forces leading an African Union offensive against al-Shabab.
American citizens, including a 26-year-old woman from San Diego and a woman from North Carolina, were reportedly among the wounded in Saturday’s attack. Several foreigners, including a Canadian diplomat and three British citizens, were among the dead.
One nearby hospital has received at least 128 patients and performed 28 surgeries to remove bullets and shrapnel in the first 24 hours since the attacks began Saturday, according to the Associated Press.
“We have at least two critical patients currently, one with bullets lodged near the spine," M.P. Shah Hospital Chairman Manoj Shah told the AP. He added that four of the 19 fatalities at this particular hospital were children.
Interior Minister Joseph Ole Lenku told reporters that the government believed there were 10 to 15 attackers and that security forces were still locked in a standoff.
He said efforts were underway to free hostages, without giving details.
On Sunday, President Barack Obama called Kenyan President Uhuru Kenyatta to express his condolences and to declare that his administration supports Kenyatta’s effort to bring the attackers to justice.
"President Obama reiterated U.S. support for Kenya's efforts to bring the perpetrators of the attack to justice," the White House said in a statement.
Kenyatta, facing his first major security challenge since his election in March, said members of his family had been killed, according to Reuters.
Mobile phone signals began to fail in the area as darkness fell. Kenyatta, vowing to stand firm against Somali militants, was cautious about the outcome, saying chances of the siege ending well were "as good ... as we can hope for."
British Prime Minister David Cameron, confirming that the three Britons were dead, said: "We should prepare ourselves for further bad news."
United Nations Secretary General Ban Ki-moon released a statement Sunday condemning the attackers "in the strongest terms."
"This premeditated act, targeting defenceless civilians, is totally reprehensible," he wrote. "The perpetrators must be brought to justice as soon as possible."
Ki-moon, who stated that he has been in contact with Kenyatta, expressed his solidarity with Kenya and added that he grieves for the families who have lost loved ones.
Ghana’s President John Dramani told the Agence France-Presse that celebrated Ghanian poet Kofi Awoonor, 78, is among the slain and expressed shock over his death. Awoonor’s son was wounded in the siege.
“Such a sad twist of fate,” Dramani said to the AFP.
Manish Turohit, 18, who hid in a parking garage for two hours before leaving in a line of 15 people who exited with their hands in the air to avoid being shot, told al-Jazeera that gunmen carrying AK-47s and wearing vests with hand grenades on them stormed into the mall.
"They just came in and threw a grenade," he said. "They were shouting and firing."
A North Carolina woman told NBC affiliate WAVY of Portsmouth, Va., by Skype that she was at the Westgate mall for lunch when the attack began.
"We stood up and started to turn, and we heard machine guns," said Bendita Malakia, 30, of Elizabeth City, who had moved to Nairobi in July to work at a financial company. "Then, we started to run and there was a second explosion, which knocked us on the ground."
Malakia said she and a friend took shelter in a store with dozens of other people, and the store manager pulled down gates to block the attackers.
"While we were back there you could hear them methodically going from store to store, talking to people, and asking questions," Malakia said. "They were shooting, screaming. Then it would stop for a while and they would go to another store."
Elaine Dang, a 26-year-old woman with ties to San Diego, was also injured, according to NBCSanDiego.com.
Another unnamed witness quoted by The Associated Press said the gunmen told Muslims to stand up and leave and that non-Muslims would be targeted.
The New York Times reported that a confidential United Nations security report said two squads of gunmen attacked on different floors of the mall.
The attack is significant not only because of its loss of life, but also because it underlines the capacity of al-Shabab to launch a sophisticated attack in the middle of a key capital city, according to Rafaello Pantucci, senior research fellow at the Royal United Services Institute think tank in Britain.
“This is not a new problem for Kenya, which has been facing not only a problem from across the border in Somalia but they’ve been seeing a growing radicalization within the country as well.”
Former prime minister Raila Odinga arrived at the scene on Sunday, along with hundreds of onlookers behind a police cordon. The crowd began to cheer as a police helicopter circled overhead.
Mary Murray and Hasani Gittens of NBC News and Reuters contributed to this report.