When asked Friday if military action against the hostage takers caused the collapse, the official answered: "Yes."
The official also confirmed that Kenyan troops fired rocket-propelled grenades inside the mall, but would not say what was used to cause the collapse. The official insisted on anonymity because he was sharing sensitive intelligence information that has not been publicly released.
The top official's confirmation backs up information given to AP by another official on Wednesday, who said soldiers were responsible for the collapse which created a gaping hole in the mall's roof. That official said fired RPGs caused the collapse.
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 publicly explained what caused the floors to collapse. One official earlier suggested it was caused by a mattress fire inside the Nakumatt department store.
It is believed the collapse of the floors helped to bring an end to the four-day siege at the mall, but it may have killed hostages still inside.
The official who spoke on Friday said autopsies on bodies under the rubble will show if those people were killed by the building collapse or had been slain earlier by the terrorists. The official said bodies are expected to be found after excavation of the roof collapse begins.
THIS IS A BREAKING NEWS UPDATE.
AP's earlier story is below.
Investigators have recovered a vehicle believed to have been used by the terrorists who led the attack at a Nairobi mall that killed at least 67 people, a top Kenyan government official said Friday.
They are also building the profile of a man who warned a pregnant woman at the mall to flee for her own safety moments before Saturday's attack, he said.
Investigators are tracing the car's ownership after it was retrieved outside the mall, the official said on condition of anonymity because he was not allowed to reveal such details while the investigation is ongoing. They are looking at more vehicles that may have been used by the attackers, he said, but gave no more details.
An Associated Press reporter saw a group of Kenyan and foreign investigators inspecting a silver saloon car parked about 20 meters (yards) from the mall's main entrance on Thursday afternoon. The car's trunk was open as the investigators took pictures and notes, but it was impossible to tell what exactly they were seeing.
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Kenyan police have given little information since the attack that shocked this East African nation, saying the investigation has only just began into the storming of the mall on Saturday by Islamic militants throwing grenades and using assault rifles.
Some bodies are believed to be buried under the rubble of the mall, which will take investigators at least seven days to comb through, Joseph Ole Lenku, Kenya's interior minister said Wednesday.
The al-Qaida-linked Somali Islamic extremist rebel group al-Shabab has claimed responsibility for the attack, saying Kenya is a legitimate target for sending its troops into Somalia to fight the militants.
FBI agents -- along with investigators from Britain, Canada and Germany -- have been dispatched to investigate the crime scene. There have been no details on what the international team has found so far in the bullet-scarred, scorched mall.
The high-ranking Kenyan official who spoke to The Associated Press Friday said it was possible that some of the attackers escaped during the mass evacuation of civilians from the mall in Nairobi's Westlands neighborhood.
Kenyan authorities have since increased surveillance at border crossings and at the airport in Nairobi, he 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.
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 on the Westgate Mall, including 61 civilians and six security forces. Five militants also were killed, but questions remained about the fate of the remaining attackers and fears persisted that some had managed to escape.
Press; By TOM ODULA]
reporter Ben Curtis in Nairobi contributed to this report.
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