Chanting "Death to America," rioters on Monday stoned the U.S. convoy involved in the accident, then headed to the center of Kabul, ransacking offices of international aid groups and searching for foreigners. Smoke billowed from burning buildings.
The death toll from the unrest rose to 11, most of them from gunshot wounds, according to three city hospitals. More than 100 people were wounded.
Up to five people were killed in the accident, but it wasn't clear whether these deaths were among the tolls the hospitals reported.
Military spokesman Col. Tom Collins, in explaining the cause of the traffic accident, said the truck's brakes "apparently overheated and failed" as it came down the long hill.
"The driver, very experienced in the operation of this type of vehicle, a heavy cargo truck, applied the primary and emergency brakes and took evasive action to avoid hitting pedestrians," Collins said.
The truck hit several unoccupied parked cars in an effort to slow, but it wasn't enough, and the truck hit occupied vehicles at an intersection, he said.
"We extend our deepest condolences to the families of those killed and injured in this unfortunate traffic accident," Collins said.
The military will compensate the victims or their families, the spokesman said, adding that a full investigation is still under way.
The crash sparked the worst riots across Kabul since the fall of the Taliban in 2001. Hundreds of Afghan and coalition troops took up positions around the capital Tuesday to prevent further unrest, and the city of 4 million was calm as stores reopened and residents went to work.
Many expressed dismay as they surveyed the damage from Monday's riots.
"Where were all the security forces yesterday?" asked Asadullah Chelsea, who owns a supermarket popular with foreigners. "I have lost thousands of dollars of stock."
In other violence Tuesday, a gunman riding a motorcycle shot and killed three Afghan women working for an international aid group and their driver in northern Afghanistan, said Gov. Jama Khan Ahmdar of northern Jawzjan province.
The rioters claimed U.S. troops had shot and killed civilians at the scene of the accident.
A spokesman for the U.S.-led coalition confirmed there was gunfire but said coalition personnel in one military vehicle only fired over the crowd. The coalition expressed regret for any deaths and injuries, and said there would be an investigation.