Police in Kenya's capital say a large blast that injured at least 27 people Monday was probably caused by an electrical malfunction.

Kenya has been hit by a string of grenade attacks that authorities blame on the Somali militant group al-Shabab and its sympathizers.

However, Police Commissioner Matthew Iteere told reporters that Monday's blast was likely the result of an electrical fault inside a building.

The explosion went off about 1:10 pm local time in a central Nairobi business district, blowing out store windows and causing a fire. Emergency workers put out the fire and took casualties to a local public hospital.

Kenya sent troops into Somalia last October to fight al-Shabab, which it blamed for a series of cross-border kidnappings.