Kenya's interior minister said the evacuation of hostages "has gone very, very well" and that Kenyan officials are "very certain" that there are few if any hostages left in the building.
Interior Minister Joseph Ole Lenku also revised the death toll to 62. Kenyan officials earlier said 59 people have died since the siege on Westgate Mall began on Saturday, while the Red Cross had put the toll at 68, then in a tweet lowered it to 62, saying some bodies had been counted twice.
A person with knowledge of the rescue operation told The Associated Press that the smoke was rising up and out of a large skylight inside the mall's main department and grocery store, Nakumatt, where goods like mattresses may have been lit on fire.
Kenya Chief of Defence forces Gen Julius Karangi said fighters from an array of nations participated in the attack claimed by al-Shabab, a Somali group allied with al-Qaida.
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"We have an idea who these people are and they are clearly a multinational collection from all over the world," he said.
The four explosions were followed by volleys of gunfire, then a thick, dark column of smoke that burned for roughly 90 minutes. Military and police helicopters and one plane circled over the Nairobi mall, giving the upscale neighborhood the feel of a war zone.
On Sunday Kenyan officials announced that "most" hostages had been rescued. But no numbers were given. Kenyan officials have never said how many hostages they thought the attackers had, but have said preserving the hostages' lives is a top priority, greatly complicating the final fight against the attackers.