An apparent explosion ripped through a building full of small shops in the downtown area of Kenyan capital Nairobi today, wounding an unknown number of people.
The force of the blast ripped apart the one-story building's aluminium roof, but a high-rise building with a glass exterior right next to the blast did not appear to sustain major damage.
There was no immediate word on casualties or what caused the blast.
People with bloody wounds received medical care immediately after the blast, as authorities tried to usher hundreds of people in the street away from the scene.
TV images showed thick black smoke billowing out of the building in the moments after the blast. The smoke then turned white.
Al-Shabab militants from neighbouring Somalia have long threatened to carry out substantial attacks in Kenya following its decision last October to send troops into Somalia to pursue al-Shabab militants.
Kenya has suffered a series of grenade attacks in recent months, but today's blast appeared to have been caused by something larger than a grenade.
The building that was attacked housed a series of small stalls. Items for sale in the shops - like shoes and clothes - were scattered on the ground after the blast.
Police Commissioner Mathew Iteere said at least 16 people were wounded. He could not immediately say what caused the blast.
Another high-ranking police official said there were no obvious signs that the blast was caused by a terrorist's bomb.
No ball bearings or nails - lethal shrapnel packed into bombs - were found, and officials were investigating the possibility that a faulty electrical line caused the explosion.
"Let me not speculate this is a terrorist attack. It could be a wire fault," said Orwa Ojode, assistance minister for internal security.