Authorities have confirmed that deaths at Gikomba market was a result of suffocation.
According to Nairobi Regional commissioner William Thuku, the 15 deaths are as a result of inhaling poisonous gases and smoke.
Over 70 people were injured in the fire that also affected nearby residential houses.
"There is a lot of smoke and most of the people who died might have been suffocated by the smoke.. the wind was blowing really hard causing this to happen," he said.
Thuku was speaking on Thursday when he issued an update on the search, rescue mission.
"Most of these buildings were housed in shops where they store flammable materials and hardware. We are aware that that is what made the fire to spread in other buildings," he said.".
Bursting gas cylinders made it impossible for the fire to be contained.