This photo released by the Kenya Presidency shows the collapsed upper car park of the Westgate Mall in Nairobi, Kenya Thursday, Sept. 26, 2013. Working near bodies crushed by rubble in a bullet-scarred, scorched mall, FBI agents continued fingerprint, DNA and ballistic analysis to help determine the identities and nationalities of victims and al-Shabab gunmen who attacked the shopping center, killing more than 60 people. (AP Photo/Kenya Presidency)
NAIROBI, Kenya (AP) — Kenya's military caused the massive collapse of three floors of Nairobi's Westgate Mall during the terrorist siege in which at least 67 people died, a top-ranking government official said Friday.
The account in an interview with The Associated Press, comes ahead of the release of findings from an ongoing forensic investigation into the attack and raises the possibility that the military may have killed hostages in their rescue attempt. An undisclosed number of people are reportedly buried in the rubble.
The official said autopsies will determine if any bodies found there were killed by falling debris or had been slain earlier by the terrorists. The high-ranking police official spoke on condition of anonymity because he was not authorized to divulge sensitive information.
U.S. Ambassador Robert F. Godec said the United States is concerned about the specter of more violence from the Somali Islamic group, al-Shabab, which claimed responsibility for the attack.
"Obviously they do pose a threat and it's critically important, I think, that we understand al-Shabab, understand what the terrorists in that organization are up to, how they carry out attacks and really seek to frankly end the threat that the organization poses," Godec said in an interview with AP "So we are working very hard with Kenya, and other countries, to do so."
FBI agents —along with investigators from Britain, Canada and Germany —have been dispatched to investigate the crime scene. Many of the dead were foreigners.
The senior Kenyan police official also confirmed that Kenyan troops fired rocket-propelled grenades inside the mall, but would not say what was used to cause the collapse or whether it was intentional. The account at least partially backs up information given to AP by another official on Wednesday, who said rocket-propelled grenades fired by soldiers created a gaping hole in the mall's roof and caused the floors to collapse.
Investigators, meanwhile, were piecing together a profile of a man who warned a pregnant woman to leave the mall just before the attack began on Saturday, the official said. The woman went home to safety. After her nephew wrote about her experience in a school essay on how he spent his weekend, his teacher informed police who have interviewed the woman about the mysterious man.
Inside the mall Friday, a baby stroller was overturned on the marble floor next to wilting fresh flowers at a florist shop. Slabs of concrete sat on top of flattened cars in the parking area while in other parts there are rows of scorched vehicles.
Four huge explosions rocked the mall Monday followed by dark smoke pouring from the shopping center, the likely time that the floors collapsed. The government has not publicly explained what caused the floors to collapse. One official earlier suggested it was caused by a mattress fire inside the Nakumatt department store.
Amid the possibility that some of the attackers escaped during the mass evacuation of civilians from the mall in Nairobi's Westlands neighborhood, Kenyan authorities have increased surveillance at border crossings and at the Nairobi airport, the senior police official said.
No bodies have been retrieved from under the rubble since Kenya's military secured the building on Tuesday, he said, adding that police are also investigating if the attackers stored ammunition inside the mall hours or even days before the attack.
A car has been discovered that is believed to have been used by the terrorists who led the attack at the mall, the official added. Investigators are tracing the car's ownership after it was retrieved outside the mall.
Joseph Ole Lenku, Kenya's interior minister, said at least eight suspects are being held over the attack. Three others who had been detained were released.
Kenyan police have given little information since the attack that shocked this East African nation, saying the investigation has only just begun into the storming of the mall on Saturday by Islamic militants throwing grenades and shooting assault rifles.
It will take investigators at least seven days to comb through the rubble of the mall, where some bodies are believed to be buried, Lenku has said.
Al-Shabab said it carried out the attack because Kenya sent its troops into Somalia to fight the militants.
The Kenyan Red Cross says 61 people remain missing and many worry their bodies may be buried in the destroyed part of the mall — though the government has insisted few victims are believed to still be inside.
The government says at least 67 people were killed in the assault by 12 to 15 al-Shabab militants, including 61 civilians and six security forces. At least five attackers also were killed.
Kenyans are still looking for answers. Lots of them.
A user-generated list of questions circulating on social media has questions like "How many terrorists were involved in the attack?" ''Are any terrorists loose in the city?" ''Can we see the bodies of the 'neutralized' terrorists?" ''Are we still safe?"
The online list reflects a broader frustration within Kenya over the lack of information surrounding the attack and questions about authorities' commitment to answering them.
There is still no precise death toll, no word on the fate of dozens who remain missing and no details on the terrorists behind the attack. Unclear, too, is how the militants were able to sustain their attack as long as they did and why a large chunk of Nairobi's most upscale mall was reduced to rubble.
Among the nagging questions are the fates of what were initially thought to be dozens of hostages stranded inside the mall after Saturday's raid. Kenyan officials said Tuesday that they believe all hostages had been "released."
The Kenyan Red Cross identifies "increased public anxiety on account of missing persons" and "inadequate information flow" among its biggest challenges.
Questions are being asked elsewhere too.
Boniface Mwangi, a photographer who has emerged as one of Kenya's leading political activists, said he believes the lack of a clear accounting of what happened at Westgate Mall is due to the government trying to paper over shortcomings in its handling of the operation.
"They're trying to cover up something," he said. "If it's true you have nothing to hide, let's know what really happened."
Kenya's Citizen TV aired a segment Thursday night dubbed "Truth under the rubble" that highlighted some of the authorities' mixed messages and unanswered questions about the attack.
For the families of those who lost or are still searching for loved ones, the lack of clear reckoning of what happened Saturday is all the more difficult.
"They're not giving us enough information. They're trying to hide a lot of things," said Roy Sam, whose brother, 33-year-old Thomas Ogola, was killed on the first day of the attack. "There must be more dead than the figure they are giving out."
Associated Press reporters Ben Curtis, Rodney Muhumuza and Adam Schreck in Nairobi contributed to this report.